ratedrookie

A few days ago I was driving my car and it was running just fine. After driving about 30 miles of mostly highway road, I exit to drive home and suddenly the car surges and dies. I am able to restart, but the engine is now running very rough and every time I put the car back into gear, it stalls. I barely managed to drive it home having to keep the engine revved to keep it running and even that didn't always work.

I just replaced the distributor cap, rotor, and ignition module last night, but had no affect on the car. It will start, but run very rough, surge, and stall. If I try to put the car in gear, it will stall. Unfortunately, the check engine light is not on to give me a clue to where the problem might be.

I also bought a new coil that I plan on installing tonight to eliminate that as a possible issue. Spark plugs and plug wires have about 10K miles on them so I doubt they are the culprit, but I may have to check them for cracks/burns anyway. I will also check for any major vacuum leaks that could cause this.

Are there any common areas that develop vacuum leaks on these engines that I should look towards? Could this be symptoms of a bad IAC valve?

Should be noted this is a '90 TBI with 107K miles.

I need to get this car running asap so any help is greatly appreciated.

DLV555

iTrader: (1)

How does it run when you rev it up? You may have a faulty IAC. It doesn't sound like an ignition problem to me. You may also have a sticking EGR valve.

ratedrookie

When I hold the revs it feels alright. It seems like when I can get it moving, it will run decent if I can hold at least 2K rpm, but once I let off the gas pedal it starts to surge and die.

ratedrookie

I still have not corrected this problem and I am running out of time to get this done.

Aside from the cap, rotor, and ign module, I also finished replacing the fuel filter, some vacuum lines, the TB gasket, and installed a new IAC valve. I did the IAC re-learn procedure and the car is still not right.

On a cold start it's barely able to hold idle, but it seems like it's slightly better once the car is warm.

It starts up fine, but then the engine will surge from around 100-200 rpm to about 1000 rpm. Once I put the car into gear, it will want to die. I'm not really sure how to check the fuel injectors, but they are spraying a cone pattern that hits the side walls of the throttle body, which I believe is what they should be doing. Also, when the engine surges, you can see the fuel pressure increase and the injectors will spray more fuel to keep the engine running.

RFmaster

Check for a stuck EGR valve. Get a vacuum pump and verify that EGR moves in and out. Better yet, remove, inspect and test off the engine.

//RF

mrcamaro1956

take out the distributor and check for any worn areas i had the same exact thing happen to me. on mine the inside shaft bearing was worn and chewed up the contact points .this cause me to think my tranny converter was no good . i hope this helps
----------
just taking of the cap wont help you you got to remove the distributor to look for any play in it .look at all 8 contact points seeif any are worn . let me know if this works

Decayed312

iTrader: (2)

im interested in what fixes it, my car was doing this and it turned out my fuel pump was going. i replaced it and the car ran 200 miles fine, put in new gas again and the car is doing it again. let me know what you do if you find the fix

ratedrookie

I have taken out the distributor and checked all the points and it seems fine. Cleaned it out as much as I could and put it back together, but same problem persists.

I also pulled off the EGR valve and cleaned all the crud and re-tested to no avail. The diaphragm was moving as it should so no problems there either.

I've been doing plenty of research on this problem all over the internet and found this piece of information regarding a similar stalling and rough operation issue:

"The [fuel pump] relay allows full fuel pressure until an oil pressure signal is detected - if none detected it shuts the engine off by killing the pump. The other possibility is a faulty oil pressure sender as oil pressure is needed to keep the fuel pump on through the relay."

I have had a faulty oil pressure gauge for a little while now. It tends to bounce around and it seems to have gotten worse lately, but I can't say for sure since the car is not my daily driver. Hopefully the statement above is true. I replaced the fuel pump relay yesterday and I'm going to swap out the oil pressure sender/switch tonight if I get the chance.

RFmaster

That is not true - In GM EFI (TBI &TPI) applications oil pressure switch has normally open contacts that are in parallel with FP relay contacts. When you start cranking engine over (i.e. <400 RPM) dizzy is sending DRP pulses to ECM which together with starter cranking enabled input force ECM logic to enable FP relay - to energize fuel pump circuit. Once starter is disengaged and engine speed is above 400 RPM and DRP pulses are continuously are being received by ECM the fuel pump relay circuit is kept energized. Once engine is running, the 6PSI oil pressure switch closes its contact as well. Oil pressure switch is a back up to the FP relay in case it fails. It's poor attempt at redundancy, but at lest its something.
If engine stalls, or if DRP pulses are no longer received by ECM fuel pump circuit and injector circuits are disabled.

Getting back to your original problem. Check reluctor coil inside dizzy and see if any of rotor magnets are missing. Measure reluctor coil resistance with a DVM across two pin connector - it should be 500 to about 1500 Ohms. Look for intermittent readings, etc. Check and see if any of the magnets are cracked or missing.

//RF

ratedrookie

I've already taken the distributor apart and did not notice anything out of the ordinary. I might go ahead and replace the pickup coil just to be sure.

I also checked the voltage to the TPS and got 0.66 with the blades closed and ~4.20 with the blades open. Are these values within factory spec?

RFmaster

Yes, 0.66 at idle and 4.2 to 4.5 V at WOT.
Before yanking dizzy again perform coil resistance check as outlined in the earlier post.

Replacing reluctor (aka pick-up) coil requires dizzy removal and partial disassembly.

Take out dowel pin from cam gear (not shown) and slide shaft out of the dizzy body. Note that your dizzy may be of a different construction, but basically the same.


Gently pry retaining ring of the shaft. Replacement reluctor kit may have a new retaining ring - take a look if it does when picking it up from parts house.



//RF

Saber

iTrader: (2)

My car had a similar problem, surging at cold start and almost wanting to die, when it would warm up it would be fine until i threw it into gear, sometimes it would be good for a drive, sometimes it would die, but upon a restart it would drive away fine. Turned out to be a Coolant temp sensor. Try testing that out and seeing if that checks out 100%.

ratedrookie

Just finished doing this and still no luck. Car starts up fine, within 1 second of cranking, but it doesn't want to stay running. As soon as I lift my foot from the accelerator pedal, it will die or surge several times before finally dying. I just got a code 34. According to the manual it's MAP (Volts LO/Vac HI). Maybe this gives me something to go on, but I could have swore I already checked the MAP sensor and it was getting about 4.96-4.97 Volts with the key on.

RFmaster

Do you get between 1 and 2 volts at idle (about 35 kPA) when it idles???


Check MAP Inlet - those crack with age and may cause vacuum leaks. Key on test just indicates that it reads about 100 kPa which is atmospheric pressure. To check MAP get a vacuum hand held pump, with key on measure voltage - at about 20 to 18 in-Hg MAP should have about ~ 1.0 Vdc. As vacuum level drops voltage should increase to about 5votls DC. For more information see below:

https://www.thirdgen.org/forums/tbi/...or-review.html

//RF

ratedrookie

First of all, that would be almost impossible to do since the car is not holding idle. It starts up then dies. Second, I didn't perform any of those tests, however, I was able to grab a brand new MAP sensor to test and the problem persists so I re-installed the old MAP sensor and returned the new one. The manager at my local parts store is a nice dude so he basically let me "borrow" a new MAP sensor to test.

Any chance that this problem could be related to the fuel pressure regulator? It seems like I've exhaust nearly every other possible issue. A former Pontiac mechanic told me that the injectors are the problem, but whenever I watch the injectors they seems to be spraying an even cone pattern. Since injectors are $100/ea at my local parts store, I'd like to be certain before I blow $200 on a new set.

Thanks everyone for the continued help on this issue.

DCOWBOYS1975

Mine was doing the same exact thing. It ended up being a vacuum leak. Mine was the opening on the front of the carb. I capped it and it purrs like a kitten. Check your vacuum.

RFmaster

Well it is not a MAP sensor - hand vacuum pump is the easy way to check MAP sensor if the engine can not hold idle. Regarding pressure regulator - you can check it with a fuel pressure test set. TBI system does not have a test fuel pressure port. You can rent FP checker from better parts stores, just make sure that it has TBI specific adaptor. Stock TBI is happy between 11 and 14 PSI.

Have you checked TB to intake gasket??? This gasket is notorous for vacuum leaks - rough idle.

//RF

ratedrookie

If a coolant temp sensor was bad, wouldn't the temp gauge in the dash be off? Where is it located and how can I test it?

I have already checked vacuum. I think there are 3-4 vacuum lines on the front of the TBI unit and 1 in the back and all seem fine. I sprayed a bunch of carb cleaner around all the vacuum lines to try to find something and I ended up replacing a couple of lines going to the MAT sensor and the TBI -> Intake Manifold gasket. After replacing those, I can't find any more leaks.

DCOWBOYS1975

OK I don't know what is causing it but I know the solution. Rip that engine out and drop a GM Goodwrench 350 that is all carb!!!!!!

tonkpils1769

mine was just having a similar problem, but my idle would surge up and down, but the car would not die on me it would run fine while driving but in park or neutral up and down all the time i went to autozone got error code 33 MAP sensor bought MAF cleaner sprayed it and all connectors and bam that fixed my problem

titchener

If you are seeing a normal looking cone pattern from the injectors and they don't dribble gas when the key is first turned on then I doubt your problem is your injectors. Double check to make sure they're not dribbling fuel when the key is first turned on. If so, it's more likely a bad o-ring than a bad injector.

If you haven't checked fuel pressure do that next, to be honest this is one of the first things you should check when an engine starts running funky. It could be a bad fuel pump, bad fuel pump harness or relay, busted spring in the regulator, collapsed pump inlet tube or plugged fuel return line. Check that pressure.

Paul T.

entrig00

iTrader: (1)

Hey people...wow for those of you guys that are helping out I just want to say wow...great info that I'm soaking up and using on my Camaro. I'm having the same problem. You guys are also helping me out as well. Thanks for the great info and I'm working on mine as well.


entrig00

Saber

iTrader: (2)

The coolant temp sensor is located near where your upper radiator hose connects to the intake. You cant miss it. It has a sensor plug going into it. Its on the front left side when your lookin at your engine, at least it was for my 305 TBI, and no the temp wont be off, my car would never warm up enough to show a correct temp anyways when i had this problem, like i said on the days when it would start fine it would get up to normal op temp and run good till the car was turned off and restarted. To check it im sure you can use a volt meter, because it should be gettign soem kind of volts im assuming, maybe someone else can help with that, but for my car i unplugged it before start up. It started up and ran fine, i let it idle and than turned it of. Waited about an hour than started it up with it plugged in. It idled like crazy, surging like a mad man, I than unplugged it while the car was started and the surging stopped, drove to pep boys, paid 11$ and threw a new one on there, watchout though if it is your CTS make sure your engine is cold cause i had some hot *** collant bubble up on my hand when i took it off. Stupid me lol. But i talked to my uncle about it when i was trying to diagnose the probelm similar to yours and he said that the car uses the collant temp sensor to know how much fuel/air to let in on a cold start and it was basically flooding the engine or something crazy like that. Hopefully that helps but i cant guarentee its the problem.

ratedrookie

Unfortunately I don't have the TBI fitting to check fuel pressure. I called several local auto parts stores and none of them have it either. The only way to get it would be to buy a whole new fuel pressure gauge that comes with the TBI fitting, but that costs $60 and I don't need the whole kit, just the TBI fitting. Also, I did replace the Fuel Pump Relay and it made no difference.

I did replace the Coolant Temp Sensor and it also had no affect.

I am officially at the point now where I am completely dumbfounded, but a few observations worthy of note:

1. The only way I can keep the car running at idle is to pull the vacuum hose off the back of the TBI going to the MAP sensor. As soon as I put the vacuum hose back on, the engine will stall and die or if I leave the vacuum hose disconnected and put the car in gear, it will die.

2. Since I need the car to run in order to move it from tow zones twice a week, I'm pulling the TPS connector to force the car into limp mode. Aside from running rich (of course), it does run fine without stalling or dying.

Do either of these provide any clues to the culprit of the problem? Continued appreciation for any and all help/info provided

RFmaster

Do a simple MAP test - ignition on, engine not running - measure MAP sensor voltage output. It should be around 4.5 to 4.8 Vdc. ECM needs to know what is the atmospheric pressure. If you are not getting this voltage MAP is a goner. //RF

ratedrookie

Have already done so, and yes, it does have between 4.5 and 5 volts. Matter of fact, as already stated earlier (I know this post is becoming somewhat convoluted) I tested a brand new MAF and it made no difference.

RFmaster

Ok, lets summarize:

MAP sensor is OK (you got a new one)? - 4.5 Vdc with engine off, but can not verify what it reads when engine is running (at any speed) - If MAP supplies 4.5 volts all the time engine will run super rich (ECM sees low intake manifold pressure which corresponds to high load

TPS sensor checked out OK. At idle it reads 0.66 Vdc and 4.2 - 4.5 Vdc at WOT

CTS sensor is new per your earlier post. Check voltage on the yellow lead - It should be between 1 and 2 votls with engine cold - this value is approximate. You can directly measure sensor resistance by disconnecting harness from sensor and inserting DVM test leads into sensor socket. DVM should read 2.7kOhm at 25C and 330 Ohms at 80C.

EGR valve - this may be stuck wide open and causing rough idle. Disconnect vacuum hose form it see if improves idle. R&R EGR valve- make sure that plunger moves when vacuum is applied and returns back to its original position when vacuum is removed. Clean out crud in the EGR port (in the intake manifold passage)

AIR actuator valve maybe leaking - this unit is connected in parallel with EGR and engine vacuum is supplied from lower left vacuum TB port when viewing form the front of the engine. Disconnect and plug TB vacuum port.

PVC valve - check if plunger spring is good, check hose.

Check if Power Brake booster is not leaking. PB booster vacuum is supplied from a tap near dizzy in the back of the intake manifold. It is rare for them to go - but does happens occasionally. disconnect and plug.

//RF

theman

in your fuel tank there's a small rubber hose thats connected from your fuel line to the fuel pump.its held on with two plastic clamps. that rubber hose is dry rotted change it . it will cause your car to stumble die idol up n down.and youll have to feather the gas to keep it running. so go spend a buck on a peace fuel line n fix your car. get back to me n let me know.or if you have any questions about a quick change fuel pump

theman

its a small rubber hose in your fuel tank thats connected from your fuel line to your fuel pump. its dry rotted.change the fuel line its held in there by two plastic clamps.it will cause your car to stumble, die, idol up n down n youll have to feather the gas to keep it running. get back at me n let me know.or if you have any questions about a quick change fuel pump.

89IROCZ28

iTrader: (14)

I was dealing w/ a similar problem and after chasing one wild goose after another, it ended up being a bad CTS.

I finally found the CTS was causing the problem by simply disconnecting it, starting the engine, and then reconnecting it. With the CTS disconnected, the engine would run, not great, but better than it had been. As soon as I would plug the connector back into the CTS, it would start running rich & rough. Disconnecting it caused the engine to run better again.

The resistance of the bad CTS is was ~10k cold and increased to ~30K as it warmed up (opposite of what it should do). As a test, I jumped the CTS connector w/ a 270 ohm resistor (I read 200 ohms is suppose to be around 200 F) and, although it was little struggle to keep it running when it was cold, it ran better & better as it warmed up. I figure the bad CTS was telling the ECM the engine was really cold, so the ECM was calling for a lot of fuel causing it to run extremely rich & rough.

The new CTS measured ~3K cold. Check your new one to make sure it's good.

Ruiner

he already said he replaced the CTS

until he can hook up a fuel pressure gauge to know for sure I say it's a fuel system problem. Either it's a bad regulator, the fuel pump is dying, or, more likely, the rubber hose inside the tank has turned to black goo

89IROCZ28

iTrader: (14)

C'mon, you've never bought a bad part? I'd check it just to make sure it's good is all I'm saying.

91RedRagtop

I keep reading on here about rubber hose problems near the tank . You just "said in the tank " ????/ I have been having a surging idle and hesitation on part throttle problem with my 92 305 TBI car .But I can look at my tank area and see 4 rubber hoses running up to the pump area from the hard lines .Is this the same area your talking about , or is there one actually in the tank itself , that gets bad ??

theman

yes it's the rubber hose inside the tank. it's only an inch long or so.you have a few choices.you can pay to have it towed to a shop.have them replace the fuel pump n charge you a few hundred dollars.or you can drop the tank yourself . take a chance on breaking rusted bolts .and well you have a look under there its not a fun job.or pull back the carpet in the trunk area n perform surgery. squarely in the center of the hump is were your fuel pump is under the metal . witch you will half to peal back.be carefull not to cut into the tank.a pair of pliers works good after you get a hole started its just like opening a can.after u open her up you'll see the 4 steel fuel lines leading into the tank . your going to cut those with a hack saw slowly.then pull the unit out. i have a nice door to my fuel pump.that dosn't get water or exhaust fumes inside and looks good to. i changed my map,cts,egr,oxygen sense,fuel injectors, idol control,iac before going with my gut instinct.

RFmaster

...after looking over this whole thread I tend to incline that a fuel pressure check is in order. Based on experience in tank rubber lasts on an average 15 years. After that you are running on a borrowed time. Check fuel pressure - there was another thread were all sensors were replaced and problem still persisted until fuel tank was dropped and rotten rubber hose between FP and feed through repalced. //RF

theman

that's right i think i threw 7 codes when i hooked it up.the first was m.a.t.mass air temp,cts, oxygen sensor,egr,map sensor,and two other codes that kind ruled each other out.one read too high the other too low. i then rebuilt the tbi changed cap wires&plugs. still nothing towed it to pinigar chevrolet told them to change the fuel pump.they refused charged me 400 dollars for shityer plugs n wires that i just replaced. pinigar wanted to change everything i put on there and replace the manifold & tbi for a carb about a 2000 dollar job all together with no garenteez. so i told them to get ****ed & did the job myself. a replaced the rubber hose in the tank.now it runs fine.pinigar will also charge 10,000 dollars for a g6 sun roof. for less money you can buy the car. i had the same problems as the kid that posted this i puting my money on the hose.wich he'll probably just replace the whole fuel pump

matchbox

I am having the same problem and took the fuel tank out and the sock was shot.

ratedrookie

I haven't posted in a while because I wanted to check the fuel pressure, which turned into an adventure all it's own. Since the POS TBI system does not have a schrader valve for checking the pressure, I had to order a TBI adapter. Only problem, I was sent the wrong part. So about 2 weeks after I first ordered the adapter, I finally had a piece with the correct threads.

Finally I tried connecting the adapter to the fuel line and there was no way to make it fit. The piece was hitting the egr valve and the hard fuel line was not going to move back far enough to thread into the adapter.

I then tried to check the pressure from underneath the car by the fuel filter. Much easier to move pieces around to make the adapter fit. I go to put on the fuel pressure gauge and the schrader valve from the adapter breaks off. That's right, the schrader valve on the TBI adapter broke off before I had even tightened the fuel pressure gauge. This was all done by hand.

So I had to repair the adapter and try again.

Finally I get everything connected and turn the key on, 0 PSI. I am able to start the car and it runs for a few seconds before dying, but still shows 0 PSI.

How can the car start while showing 0 PSI of pressure? I checked the gauge on another car and it works fine so I'm not sure what the heck is going on. I thought it might be the TBI adapter, but it's working since there is fuel going from the schrader valve to the gauge. If I relieve the pressure from the gauge, gas pours out of it, but still shows 0 PSI.

91RedRagtop

Wow man that sucks . I just want to say that I was having a problem with surging idle and bucking on takeoff . Checked fuel pressure and had 4 psi . Took out the tank and the little 1 inch hose connecting the pump to the hard line had a half inch slit in it . Replaced that and the pump and she runs like a champ .

Raiderfan

I'm having the same exact problem with no luck. My next step is to replace the fuel pressure regulator, I hope that works........

Camaro_640

Ive never had a coil Go bad with the Lower RPMS... Just in the Higher RPMS... the dwell becomes too much to handle up in the higher RPM with our coils..

How many Fuel injectors are Firing? Both or just one?

Color of the plugs?

ratedrookie

The issue has finally been resolved!!! Brand new AC Delco fuel pump and the car is running fine. After I was finally able to check the fuel pressure it became obvious, although I found it extremely odd that the car would start and run for a couple of seconds with 0 PSI of pressure showing on the gauge.

However, not all is perfect. I had an erratic oil pressure gauge so several weeks ago I installed a new oil pressure switch/sender. The next morning my battery was dead. Did some checking and realized that when the new oil pressure switch is plugged in, the fuel pump stay running all the time. When I pull the connector from the oil pressure switch, the fuel pump turns off. Did the parts store sell me a faulty oil pressure switch? For the time being, I unplugged the oil pressure switch so I wouldn't have to keep disconnecting the battery.

RFmaster

ratedrookie

Thanks for update. -Another FP problem caused a lot of PITA. We could only wish if GM made it easy to check Fuel Pressure on TBI setups.

It is all too common for new (electrical) parts to be
defective straight out of the box. Quality control is not what it used to be, as most manufacturing is done in the far east where they do not give a @$#_( about quality. As long as volume of parts delivered to is maintained all is good.
//RF

bigd077770

please read my post "it wont run!" had many similar problems and many people tried to help . thanks , just pulled out fuel pump and little connector hose was a big puffy ball of jelly. it woukld pump enough to start but wouldnt build any pressure to keep running. will replace and see .Thanks

Chris67rs

wow what a read, I have a similar situation but exact opposite, My 91 formula 305tbi runs GREAT, but hard to start, I can run it all day long dog the crap out of it, it idles fine, unless you put it in gear, then it conks out, if you powerbrake a little bit to keep the revs up around 650-700rpm its fine, thought egr, all the IAC, CTS, MAP, Fuel filter, pump, etc,

looking though all the advice above, I dont need the fuel pump as I just changed it about 1000 miles ago, (Ac delco, not that chinese crap for 40bux at autozone) new sock sleeve, plastic case thing was all one unit, brand new, I have 6.2 lbs fuel pressure, wonder what mine is... clogged cat converter?

titchener

Are you sure the fuel pressure is that low? TBI cars should have pressure of 11 to 12 psi right at the inlet. If your pressure is really that low it would not only idle poorly but also wouldn't run very well.

Low pressure can be caused by a cracked regulator spring or faulty regulator diaphram. Also a bad fuel pump relay, corroded pump connectors/wiring, a split tank fuel hose (pump to outlet) and plugged tank venting can also cause low fuel pressure.

Paul T.

Raiderfan

These cars will run and drive on 1-2 psi of fuel pressure.
Don't waste your time on parts that don't need replacing.

I had 2 lbs of fuel pressure with the same symptoms, the last thing I checked was the fuel pressure. I had the pump replaced and it's like a brand new car......

inittab

Hello. I'm having some of the same issues mentioned in this thread and wanted to test the Fuel Pressure on my 350 TBI.

is this what I need?
http://www.amazon-auto-accessories.c...ffId=the004-20

Also does anybody know if auto zone, advance auto parts, or napa would have what I need? I rather get it local than order online. Thanks.

89IROCZ28

iTrader: (14)

It sure looks like a nice kit. Wish I had come across that when I was having problems. I ended up permanently installing a gauge in the pressure side rubber line between the chassis and hard line that runs from the front of the engine (LO3) and throttle body.

As long as that adapter fits the pressure side fitting on the throttle body (which it looks like it's made to do), it'll work great.

slayernut

I have had the same problem for over a year now, tried everything, all new sensors ect" ect". I have never figured the fuel pump as it seems to be getting lots of fuel to the injectors but have never tested it. I have constantly got my hopes up with the next sure fix everytime, only to be let down again. I am heading out right now to buy a new pump and hopefully wont be let down again...lol..... Oh crap i'm getting my hopes up again lol.