amitchell

I bought this 1991 firebird in like Oct 2012 and I finally getting around to working on it. The previous own told me he did a tune up on the vehicle then he started having problem with it stalling out on him after in runs for a few minutes. He then did another tune up fix the problem for a few weeks then it did it again. He took it to his mechanic who told him he was having a timing problem and had that the chain slipped, he started to replace the timing chain but then the old owner told im not too becuase he could afford it. He let it sit for a few months and this is when I bought it for $600.

Problems it had:
Car started only twice and would run for about 5 seconds then shut off. Ran really rough for the few seconds.
Gas mixed with oil in Oil Pan when i drained it.
When car was at TDC the distributor rotor was at #4 firing postion.

Codes: 12, 15, 43

What I've done:
New Battery
Oil Change
New Knock Sensor
Added Sea Foam to Gas
Replace Fuel Pump Fuses wasn't working when tested before (I hear fuel Pump running when key is in on position)
New Fuel filter.
New Water Pump
New Timing chain, Set the timming manually (since wont run) by turning crank manual to TDC. I then repositioned the Distributor and rotor to make #1 in firing postion:

Now Code 12, 43

Still cranks but doesn't want to turn over. I now hear like a slight backfire or pop in the exhaust.

vetteoz

iTrader: (13)

Around here ; cranking is TURNING over ,as in ; the engine is rotating, spinning ,turning ....

What you are describing is NOT FIRING UP

Which TDC ; there are two ?
If you used the wrong TDC , the dist could be out be 180 degrees which could account for the backfiring from wrong timing

amitchell

I reset the timing again. I think I was 180-off. I got the engine to run for about 10 seconds. However I ran very rough just like before, before it turn off. I got it to also crank another3 times for about 3-5 seconds each time. Afterwards through the code reader on and got code 12, 43 and I welcomed back code 15.

I think i drained my battery in the process of trying to get the car to run like 20 times.

ASE doc

Code 15 is ECT sensor reading low coolant temp. This code usually comes up when the ECT sensor is open or disconnected. This will cause the engine to run very rich and explains the high fuel content in your oil. The firing through the intake sounds like timing too retarded or plug wires crossed. Who did the timing chain? Are you sure it's installed correctly?

Verify that the ECT sensor is connected first, then test it for resistance. It should read 3,400 ohms at 70 degrees, as on a fully cold engine. Once you have that problem solved, recheck engine performance.

Code 43 is ESC knock sensor circuit and could mean the ESC system is retarding timing a constant 18 degrees due to a fault in the system or that it's picking up engine noise and retarding timing trying to stop engine knock. Either way engine performance is going to suffer. A scan tool is needed to diagnose this code.

amitchell

Code 15 no longer showing after I checked it again. I installed the new timing chain and I'm pretty sure its installed correctly. There is no difference of operation or change of symptoms between from what I've done to the car compared to when I first got it besides it has a new chain on it and new knock sensor.

ASE doc

To diagnose a "cranks but won't start" symptom, you first need to verify spark on at least two spark plugs. Then verify timing with a timing light while cranking. You either need a helper or use a push button starter. Timing of about 8 degrees BTDC, or whatever base timing spec is, should start the motor okay. Once you verified spark and timing, look at a few plugs. Are they wet? If so, do they burn off with a lighter? Do they smell like fuel or are they wet with oil or coolant? If the plugs are dry, verify fuel pressure while cranking, if pressure is okay, verify injector pulse on both banks.
Disconnect the two connectors from the ignition coil and crank the engine. Does it crank smoothly? Or does it sound like a few cylinders are low on compression?

If you have fuel of close to the right amount, spark at the about the right time and plugs aren't fouled with fuel or oil, and you have compression, it has to start. The two cases where I've had engines fail to start with of these things verified, had clogged, and I mean completely clogged, exhaust. I had that happen, as well as I remember, twice out of at least a thousand cranks but won't starts that I've diagnosed and repaired.

The 3.1 is an interference engine and if the timing chain jumped very much, you will have bent valves. This like crossed ignition wires would explain the backfiring through the intake. If a couple of intake valves are stuck open, it could also make the engine very hard to start. Even one stuck open intake valve will make the engine run very rough.

vetteoz

iTrader: (13)

How did you determine TDC?

amitchell

To determine TDC I acually remove all spark plugs, inserted a hose with a squeak attached to the end of it into the #1 plug hole. Once I started hearing the compression through the hose from the squeak i continued rotating the crank until it stop and the harmoinc balance was aligned with the 0 degree mark. I then used a screw driver to make sure I was at the top by inserting it into the plug hole a moving the crank back and forth. Afterwards I put the dirstubutor, with rotor aligned with #1 wire back in, as well as all my plugs and wires.

amitchell

Note*: When I did get it to run and pressed on the gas pedal there is no pressure, or higher idle.

RBob

iTrader: (1)

Just an FYI that trips up a lot of folks, #1 cylinder on these engines is on the passenger side. That is the cylinder that is right behind the alternator.

With the firing order being: 1, 2, 3, 4, 5, 6

If the engine still has the stock OEM Multec injectors, it is a good possibility that enough have their coils shorted out that the ECM can barely open them. Any injector that measures less then 12 ohms is bad.

RBob.

ASE doc

Do you mean there is no fuel pressure? What pressure are you referring to? And, note what Rbob said above. The family of V6 engines that the 3.1 is a member of have a different cylinder layout than typical GM V engines. If you are thinking typical GM, you will looking at cyl #2 rather than cyl #1. One clue is to look closely and try to determine which bank(cylinder head) is closest to the front, which intake runner or injector is closest to the front. Which ever one is, is number 1.

If you mean that the engine idles but won't accelerate above idle, this would lead me to want to verify fuel pressure. Once I know there is sufficient fuel pressure at the rails, I would disconnect the MAF sensor and try running the engine as a quick test of the MAF sensor and circuit. (I left the MAF out of my basic description of cranks but won't start diagnosis). Also as Rbob referred to, and I forgot to mention. The injectors on the 3.1 are batch fire with two injector drivers, each one controlling one bank of injectors. A severely shorted coil on either bank will prevent that bank of injectors from opening properly. After cranking the engine, check the plugs for ones that are wet or dry. Plugs that are wet with fuel are getting fuel but no or weak spark(check the plug for cracked insulator after verifying spark to the plug). A plug that is dry is not getting fuel.

Have you tried the cranking compression test yet?(disconnect the coil and crank the motor to check for a loss of compression on one or more cylinders).

RBob

iTrader: (1)

There is a single injector driver in the '7730 ECM that the 3.1l f-body's use. It exits on two pins, but both pins go to the one driver.

RBob.

ASE doc

Wow. I never knew that. From their behavior when diagnosing them, I have always believed that there were two separate drivers. I have had one bank taken out by a shorted coil and I am sure I didn't see it take out the other bank's injector pulse, unless I'm remembering it wrong. Does the one driver separate the two channels?

RBob

iTrader: (1)

There are two injector fuses, three injectors on each. Pop one and three injectors are lost.

RBob.

amitchell

What do you mean by this? Meaning two fuses at the fuses panel or what? sorry if its sounds like a stupid question?

RBob thanks but I was good on knowing where the #1 cylinder was.

I checked the fuel pressure at the schrader valve while my wife helping me by trying to get the engine to turn over, I got a reading of 44psi while she turned the key. I did this three times and got the same reading. Afterwards the pressure would slowly go down.

I also bought a compression tester but I was not able to use it today. I will try tomorrow.

ASE doc I will try pulling out spark plugs right away as well tomorrow after trying to get it to start.

RBob

iTrader: (1)

In the fuse box under the dash, drivers side. Labeled INJ1 and INJ2. ASE doc was recalling times when three injectors were lost, this is one way it can happen. Also, the 2.8l MAF f-body ECM does have two drivers in it. So with those ECMs, more so with the '89 which used Multec injectors, it is possible for shorted injectors to only affect three.

RBob.

amitchell

Understood RBob.

I cleaned the spark plugs since they were fouled but were not damaged at all. They practically looked almost brand new. Anyways, afterwards I installed them and tried to start the car, with no change of course but I did immediately removed them after trying to start the car. All 6 of them were wet. But I am get little chunks of carbon deposits on some them.

Still no compression test yet waiting on another set of hands.

So can I assume I am not having a fuel problem yet?
Do you guys think I should add like and octane booster to the fuel. The car been in my garage since October but I did add a fuel Stabilizer to gas tank.

ASE doc

Octane booster isn't going to help anything. If you suspect that the fuel is old and has lost it's volatility, you need to empty the tank and add new fuel. That's not easy on the third gen body since it generally involves dropping the tank. I don't think the 91 has an anti syphon screen, but I don't remember for sure. You can try feeding a small hose down the fill neck and find out. Otherwise, you could use the car's fuel pump and disconnect the supply line, run it into a can and drain the tank that way. The best way I know to identify old fuel is the smell. It smells more like kerosine than gasoline.

If the motor has been badly flooded, and especially if you have intake valve damage causing air and fuel mix to be pumped back into the intake manifold, there may be fuel puddled in the intake manifold that will foul the plugs immediately upon cranking. That's one reason why you disconnect both coil connectors when doing a compression test. This not only interrupts spark but also powers down the ICM so that there is no reference pulse to the ECM and thus no injector pulse, no fuel being added to the already flooded engine.

You really need to perform the compression test at this point. You have already, I assume, verified spark to the plugs and the flooding tells us that you have injector pulse and fuel to the rails. We need to verify that the engine is mechanically fit before we spend too much time chasing ghosts. A decent compression gauge, like the KD tools unit I have, threads into the plug hole and has a check valve in it so that it holds pressure. This way you can crank the engine from the drivers seat and then go back to see your reading. To get correct results, be sure that the throttle is fully open. The KD compression gauge is probably about $40. I've had mine for 15 years and have used it a few hundred times and it still works great.

I just read Rbob's last post. Pulling the injector fuses is a good way of disabling the injectors during cranking tests. I'm sorry I didn't think to mention that. Removing the fuel pump fuse is another way.

amitchell

Compression test as follows:

Cylinder #1: 182 psi
Cylinder #2: 163 psi
Cylinder #3: 180 psi
Cylinder #4: 170 psi
Cylinder #5: 165 psi
Cylinder #6: 170 psi

ASE doc

Not great but not fatal. You have a few weak cylinders, from the unevenness likely some wear of valve faces and seats, but nothing that points to severe valve damage or that should prevent the engine from running. Now that we have verified a mechanically serviceable engine, we need to verify solid KV to the plugs. We can have spark but still have issues if the system won't support sufficient KV. Use an inexpensive adjustable KV tester from the parts store. Set it to 40KV. The HEI system should be able to produce 40KV at the plugs. If it won't, try it at the coil. If good at the coil and not at the plugs, the issue is wires cap and rotor. If no good at the coil, replace the coil. Note that once plugs have been fouled, they will not work as well as new even after cleaning.

Are you sure the fuel is good? If not, replace it with new fuel. You could try disabling the fuel system and firing the engine on alternative fuel like starting fluid. Be sure that the fuel in the tank is in good condition before you try to run the engine on it.

On a fuel injected engine there are things that can aggravate a no start. The coolant temp sensor is vital. If it is reading colder than actual. The engine will get too much fuel. The MAF sensor on vehicles so equipped, can also cause under or over fueling. As rare as I've found it to be, a completely clogged exhaust can also cause a no start. Removing the O2 sensor or disconnecting the exhaust before the cat will allow the engine to start in this case.

Maverick H1L

iTrader: (8)

Um, those compression test results are better than I was getting in my 3.1 with bad valve seals (which ran fine and got 30 MPG). Nothing wrong there.

No MAF post-89 in the thirdgen.

Last I checked, removing the fuel pump fuse also disables the ECM... Either disconnect both the pump relay and oil pressure unit OR the front injector harness connector. Or just block the throttle wide open (clear flood mode, disables injector pulse).

After checking spark (note the color of the spark), a vacuum test is in order if you can get the engine to run long enough. Check the vacuum lines and hoses for breaks and deterioration.

How old are the cap and rotor? How do the contacts look?

Do a resistance test of the fuel injectors... Probe between the pink and blue and green (pink and blue, pink and green... One pink has a stripe, can never remember which bank is which so you'll have to test). Should come up around 4 ohms. 6 or more is an issue, but you would need to run tests on the individual injectors to find out (if you're coming up with 6 ohms, each injector would be around 18 on the same bank if they are good otherwise one is probably shorted).

amitchell

I order a new distributor, cap, rotor, plugs, and wires. I was getting spark before now I am not perhaps the pickup up coil went bad. I could replace the pick up coil only but I decided to just replace everything. I also installed a new ignition coil yesterday. The other parts should be in, in a few days.

ASE doc

Maverick H1L, The reason I suggested pulling the fuel pump/ECM fuse is because, even though it will disable the ECM, the distributor will still get power and should still produce spark while cranking. INJ fuses also good way to disable fuel as Rbob suggested. The main thing for the cranking tests is to allow spark while disabling fuel, especially since the motor is flooded.

amitchell

*UPDATE*

Got new distributor today. Swapped out the old one through in the new one. Car started up right away, you can definitely tell the difference. Pressed on the gas and got the engine to rev up. However cut off after about 15 seconds or so. I charging the battery right no on car to see if thats a problem as since i been trying to get it to start I know I have been killing the battery, any other suggestions would help thanks. Got code 43 still and code 15 reappeared again (one minutes its there, the next its not)

ASE doc

Did I already tell you that code 15 is "low coolant temperature indicated"? It means that the circuit to the ECT sensor is going open. It is most likely a funky connector at the sensor. This will cause some pretty serious runnability issues. I've seen engines that would barely run with this code active. That could be your problem. Be sure to double check all of your connections at the dist.

amitchell

Charge Battery Tried starting it initially wouldn't start. Checked for spark, has spark. remove the air intanke and open the Thottle a little fire right up. Is that correct to say I have ad air problem now?

ASE doc

It would appear to be an IAC problem. You can test the valve with an ohmmeter but you can't really be sure that the stepper mechanism is okay and that the ECM command signal is what it should be without performing an IAC test. For that, you need at least a volt meter. A scan tool is helpful for watching IAC steps, commanded and actual idle speed. I use my lab scope to watch the command pattern to be sure that the circuit and drivers are all good. I also have a Thexton IAC tester that makes testing the valve itself super quick and easy. You could just try installing a new IAC valve. Be sure to make sure the passages are all clear.

I'm trying to picture what throttle body the F-body 3.1 has. The 2.8 and 3.1 in every other application had trouble with throttle shaft wear causing the TPS base setting and minimum idle air setting to be inconsistent. The test is to watch TPS voltage as you open and close the throttle repeatedly. Watch for minimum TPS voltage to change from one time to the next. The symptom of this is poor idle quality and stalling and sluggish throttle tip in acceleration.

The codes 15 and 43 will be a problem for you too if you don't address them. Code 15 will make the car pretty much undriveable if it's active when the engine is hot. Code 43 will cause a pretty serious power loss and poor fuel economy.

amitchell

Code 15 comes and goes is ver inconsistent. code 43 i have never been able to get to go away. I installed a new knock sensor yet the code still exist.

I will buy new IAC and probably TPS tomorrow

ASE doc

Code 15 means that the ECT sensor circuit is open. It's often caused by a poor connection at the sensor. I have had many occasions of broken wires inside the insulation right at the connector. You can't see the wire is broken. You have to either do a continuity test while you wiggle and pull on the wire or you can try gently pulling each wire and see if one stretches. Wire itself does not stretch, but insulation does. If the wire seems to stretch, it's because the wire is broken inside the insulation. Repair connectors with leads are available from most auto parts stores.

The test for code 43 is pretty basic, but it calls for the use of a scan tool to watch knock retard while you test the sensor and circuit. When the code is active, the ESC module commands the ECM to retard timing 18 degrees generally. This results in reduced power and poor fuel economy. On the 91, I think the ESC function is internal to the ECM.

amitchell

Installed new IAC and TPS. got the car running. It shut off multiple times as it blew out white and blue smoke. IT eventually settle down after about 30 min or more of messing with it, then it suddenly shut off.

New codes 23 and 42 along with 15 still. Then sometimes I will have no SES light.

Had to use staring fluid multiple times to to get it to turn back on. I also try to drive it down the street but lost power in the accelerator. Then started shutting off every time I hit the gas.I think Im gonna tow it to the the dealer tomorrow to let them mess with it,

ASE doc

Letting a professional look at it may be the best bet. The codes you ended up with are 23 "inlet air temp sensor, low temp indicated", which would be the sensor is disconnected or the harness is open. 42 "EST spark timing circuit" which could be related to the stalling if it is caused by a short in the EST harness. Code 15 is again, "ECT sensor low temp indicated" which is most likely the sensor circuit open or high resistance.

amitchell

Dealer ship sorta kinda check it out today, told me to replace the air temp sensor and like ASE Doc said the Coolant temp connector. The estimated a cost was $550.00 for the dealership service dept to do it, but the technician siad that was just the starting point. So in my opinion they either no more and don't want to share or they are just going to trouble shoot as well. Anyway, I said no and I towed it home and replace the sensor and connector myself.

After replace Air temp sensor and CTS connector there is really no difference. Car fired up fine, but oh wait now there are more codes than before, let me list them

Codes 15, 22,23,33,42,43,45,53.

Not sure where to go from here.

I also timed the engine using a timing light. Correct me if i am wrong but I am suppose let the engine warm up to normal op temp then shut it off. Immediately connect the timing light, start engine, disconnect EST bypass, shoot the light, correct timing to 10 degrees BTDC then, recheck timing, shut engine off, reconnect EST bypass. right?

ASE doc

Start the engine and warm it to operating temp. Shut the engine off, disconnect EST connector with engine off. Connect timing light, start engine, set timing, shut engine off. Disconnect timing light and reconnect EST connector with engine off. Disconnect battery- cable for 30 seconds to erase codes.

ASE doc

I'm sorry for your troubles. Honestly, the techs at least at the nearest Chevy dealer to me have probably not spent much time on any vehicle older than 2000, with the exception of their own cars. Dealerships do see old iron like all of us but just because your car is a GM product, you can't assume that anyone at your local dealership is going to have expertise in that early system. They are focused on gen II and III controllers and multi module CAN systems. They may not even have a Tech1 that still works.

Finding an honest technician that has real expertise in these systems is a crap shoot. That's why, if you have the aptitude to understand the science and are willing to invest in the right equipment, it is generally best to do your own diagnosis and repair. If you were close to me or any of the masters on this forum, I'm sure that any of us would be happy to help but then, speaking for myself at least, I may not be as pricey as the dealer but I don't work for free either. The assistance I offer on TGO is just my way of sharing the information that has been given me.

Having finished my rant, I will say that I don't see going much further on this car without a scan tool and some in depth circuit testing. You need to pinpoint either a failure in the ECM or its circuits. Start of course with the CTS circuit since that's what you just worked on. BTW, be aware that unless you clear DTCs by either commanding a DTC clear with a scan tool or disconnecting the battery for 30 seconds, each DTC will remain in memory and appear in a DTC check, even after the cause of the DTC is repaired. Basic tools for diagnosing these cars are a compatible scan tool and a DVOM. A 12 volt test light is also a good tool.

While I use a Snap On Solus Ultra, which with the GM-1 adapter becomes a full function Tech1 with a much better screen, for my all makes and models work, I understand that WIN ALDL works well on these cars and it is a free download. You need to make your own interface cable following the instructions they provide. A scan tool does alot more than read and clear codes. It provides vehicle specific tests and reset capabilities and it gives you a window into the ECM's logic center to see things that are not available through any other means. Things like commanded idle and actual idle as seen by the ECM, fuel trims and ECT as seen by the ECM. This information is crucial in diagnosing these systems. You also need a DVOM with 10megaohm per volt input impedance for testing ECM circuits.

You may need to test the ECT sensor circuit from the ECM to the sensor, if the code returns after code clear. A quick test you can do with the scan tool is to disconnect the sensor and verify that ECT data goes to -34 degrees, then quickly jump the two connector terminals together and verify that ECT goes to 266 degrees. This tells you that the wiring between sensor and ECM is good and that the ECM is responding to changes in resistance. If ECT data doesn't respond this way, there is an issue either in the ECM or in the circuit.

Use your DVOM to check for voltage at the yellow wire. With key on, it should read 5v. If not, the wire is open or there is a poor connection at the ECM or the ECM is faulty. Check the wire for continuity and check the connection at the ECM. Also, using a 12v test light, you can connect to ground and momentarily tap the yellow wire terminal at the sensor connector and ECT data should go high. If the yellow wire checks out, verify ground on the black wire.

A word of warning: when testing ECM circuits, don't insert anything but the correct male terminal or a small back probe into the female terminal of any connector. You'll create more problems than you solve.

Code 42 will show up anytime you run the engine with the timing connector unplugged. Code 43 is knock sensor, probably a bad knock sensor connector or wiring. The scan tool is needed for testing out this code. 22 and 23 are TPS voltage high and voltage low. These can easily be checked out with the scan tool. Code 53 is system over voltage. Have you used a battery charger on jump start? This will cause code 53 to set. Code 45 is O2 sensor rich exhaust indicated. This would go along with the ECT low temp indicated and may just be a secondary code.

amitchell

cleaned the fuel rail, Installed new injectors, re-wired the coolant temp sensor connector and new temp sensor wire. Car fired right up drove it up it down the street for a few minutes, since its not registered i really dont want to have it out. On my way to the dmv

amitchell

So i drive the car occasionally now. For a while it was running fine except for cold mornings it will loose power during acceleration than shut off on me. I was and still am stumped on this one.

This past winter i didn't drive it at all just started it up every week or two. Now that the warmer wheather has been here for a few weeks already, I have taken the car out a couple of times. With that being said on somedays it has driven flawlessly on others it has done the same with the sudden loss of power during acceleration.

dustin1984

i had same problem but mines not fuel injected i took the #1 spark plug out put finger in and have someone else turn the key when it pushes your finger out its on #1 make sure they stop trying to turn it over as soon as your finger is pushed out then put distributor rotor in the 1 position. my distributor fried becouse the ppl who worked on it before i bought it put it in 180 degrees in the wrong direction

OrangeBird

iTrader: (1)

Nope .... NOT possible ....

A distributor that is improperly timed will make the engine run bad , and if mistimed bad enough ( "180 out" for example ) it will make it not run at all ....

BUT !

There is no way possible for that to "fry" the distributor itself !

amitchell

I got my car up and running like in the while ago like last June or July. I just have problems now with lack of power somedays when accelerating, however recently it hasn't done it. What it does is sporadically it will lose power when hitting the accelerator and I will basically crawl at like 5-15 mph with a slight back fire etc, it will eventually turn off on me. Not sure why, but /i haven't been able to figure it out because its so sporadic.

RBob

iTrader: (1)

Pull the ECM down and start the engine. Now rap on the ECM case with your knuckles while listening for a change in how the engine runs. It is possible that the ECM is intermittent.

If you get another one be sure to keep the MEMCAL that is in the current ECM. It needs to be swapped into the replacement ECM.

RBob.