I have a 1990 3.1 v6 firebird, and recently been having poblems with the motor. My car's RPMs will occasionally waver very low (while Im driving) to the point that when I give my car gas it gives the feeling of dieing and losing power. Stalling completely out can only be avoided by switching the car into park and letting it sit for a while. Just recently I have gotten a check engine light come up. So, i checked it and came up with CODE 45.

According to my GM trouble codes list means the following: Rich exhaust/oxygen sensor rich error.

I recalled an odor and slight smoking out of the exhaust. Does anyone have some ideas to what might be causeing this, or some possible remedys?

 

Diagnosis via the internet can be tenuous, at best, but here's my guess anyway:

The ECM is trying to tell you something. Fortunately, it has a listener.

The typical EGO sensor (at least our zirconia types) will start showing a weaker signal (lean indication) as they age. For a sensor to fail in the rich mode is almost unheard of. From that, we can surmise that your sensor is at least working, and is likely indeed detecting a rich indication. You can probably forget about false rich indications (for now, at least).

The reasons for a rich indication can vary, but it all comes down to there being too much unburnt fuel in the exhaust gasses. That could be from excessive fuel, or could be from poor or imcomplete combustion. For that reason, you need to ascertain that the ignition system is functioning properly. If you are certain that the spark plugs, wires, coil, distributor, and timing are all reliable and correct, you can concentrate on the fuel delivery system. If not, it's time for an ignition tune up as a starting point. You should at least remove and inspect the plugs to make sure the mixture is rich. The plugs will likely show the condition. Clean or replace the plugs, and try again.

Since you have a 1990-later V-6 MPFI, you likely have the Multec fuel injectors. These early variety Multecs are very suspect, particularly in the solenoids. Mechanically, the valve design seems to be decent, and the tips appear to be good for preventing deposits, but rumor is that they do tend to suffer from solenoid coil failures. Just for that reason, you should unclip each injector's wiring harness and measure the coil resistances if you can. If you have one coil that is shorting to ground, it is theoretically possible that the remaining injectors could be going static (open 100% of the time), or at least the excessive injector current may be making it difficult for the ECM to provide a sharp cutoff of the injectors. Either condition will result in excess fuel.

Another possibility is that one oe more of the injectors is stuck open, delivering 100% fuel constantly. As mentioned, the Multec valves themselves seem to be good enough to resist this, unless the solenoid coil has melted and mechanically stuck the injector pintle open.

A failing FPR can also create a rich condition by allowing raw fuel to dump through the vacuum pilot tube to the intake. The easiest way to determine that is to remove the FPR vacuum line with the fuel pump running and monitor the FPR for fuel spillage out the vacuum connection.

Let us know how these steps work for you. We can go on from there if necessary.

 

Great. Thanks for the advice. I replaced the O2 sensor fo the heck of it, its was only 25 bucks. I saved the old one for possible future use if its OK> It seems to run fine now, but who knows. I will try all the things you suggested and report back. I already replaced the TPS, the PVC valve, the fuel filter, and reset the idle according to the proper method. Each time it seemed to work for a while and then came back. I guess it is an intermittent problem that I haven't found yet.

 

We have replace the plugs. They didn't look to bad to me, although Im not exaclty sure what to look for. I assume that bad would be black and buildup all around the spark contact point area. I got the car last summer so I am just replaceing a lot of these things to be sure that they are good. I also replaced the plug wires, cap and rotor. got a new OEM coil but haven't had time for that yet.

Oh yeah , I checked the timing and the book says to jump A and B terminals to disable EST. I did that but the timing still showed like 20 deg btdc. According to the book it should be like 10 deg. I am not sure I have disabled EST because 20 would be way out. I tried to loosen distributor but the holddown bolt appears to be 15 mm and all I have in distributor wrenche is 9/16 and no auto parts store around here had a 15mm.

It seems to be running fine, but it did that before and then messed up again.

Also, what is the proper method for checking injector resisitance?
I assum it is sticking one prove into the clip, and then the other on the motor for ground. What should the resisitance be? If it is zero, then there is a short right?

thanks again. I need to get it going to go to school.

 

to check the injectors. you have to pull the harness connectors off, under the connector in the injector there are 2 terminals, measure the resistance between the terminals. i think the resistance is around 16 ohms, but i could be wrong.

also when you check the injectors, with 1 lead of the ohm meter on either terminal of the injector, put the other meter lead to the metal part of the body of the injector, it should show an open circuit that way.

 

Thank you for explaining that. The car seems to be running ok, but I will do this anyway to see if the injectors are ok. Do you happen to know what the stock rating on injectors for the 3.1 V6 are? The minimum I see in Jegs and Summit catalogues is 19 lb injectors.

 

Well Ive been driving the car for 3 days now and it has not messed up again (actually its my son's car). I have not had time to check the injectors, I will do that today, and replace the coil with the one I bought a few days ago.

this kind of problem is especially aggravating because you are never sure you actually fixed it and it can come back and strand you somewhere. Well, the only thing to do is drive and see what happens I guess. I think it may have been a plug wire or maybe the distributor.

 

Well, I finally got a 15mm distributor wrench and set the timing to about 12. As soon as we started the car after setting the timing, the loosing power thing came back. I mean the first time starting it after setting the timing. It idles, but if you give it any gas it losese power. We changed the Ignition control module and that problem went away. However, it still dies sometimes ar low rpm. It seems to idle fine, about 700rpm with foot on brake and in park, but every once in a while it just dies. We still havent checked the resistance on the injectors, Im going to do that today. Also need to regap the plugs to .045 from .035 because the hoood is from a 5.0 L and it says to gap at .035. Didin't notice that until recently

thanks

 

OK, finally got the injector resistance checked. Using a digital meter I got, in ohms, 12.6 12.6 11.0 one one side, and 12.8, 87. and 9.3 on the other side.

What are the values supposed to be?
Are some of these values far enough out to warrant replacing the injector?
Can this be causing the problem?
What is the pressure rating on these injectors? Can I get Accel ones, or cheaper ones and mix them, or do I have to replace all of them,

etc

 

87? Are you certain it is 87? The injectors at 12 ohms are fine (at least, electrically). The 11 is probably O.K. The 9.3 and "87" are suspect. If that was supposed to be "8.7", it is still suspect. While they might not be quite low enough to take out the fuse, and the ECM may be able to switch the current on to operate them, they might be drawing enough current to make the ECM output transistor have some dificulty in turning them off quickly.

Were you able to check the resistance from the injector coils to a goor ground? That would have to be performed with the ALL injectors unplugged, of course. If you measure any resistance to ground, you may have a typical Multec coil insulation failure problem. The resistance when hot commonly only goes down, not up, so the circuit will only get worse as the engine starts and runs for a while.

 

Im sorry, I didn't check my typing, yes it is 8.7 ohms. I also checked each prong of the injectors to ground. IN each case the needle did not move, in other words, infiniite resistance. This means an open circuit and I believe that is correct from prevous message. YOu are saying Any resisitance indicates a problem? I am confused about that. All measurements were taken with the injectors disconnected. Everything is currently out of the car waiting on a set of 15 lb ACcel injectors that will be here on Tuesday. The injectors on one side seemed very dirty with some kind of buildup. I replaced the coil today ane regapped the plugs to .045 instead of .035 (I had gapped them according to the hood specs which was from a 5.0 L car). I sure hope this works. My son needs this car to go to school.

 

Any resistance reading to ground can indicate a problem. Resistance across the coil winding should be in the area of 13 ohms, but 12 is more than acceptable. It appears that most of your injectods are servicable (at least electrically) but two of them may have coil insulation that is breaking down. One (at 8.7 ohms) may be low enough to start causing problems already.

A new set should eliminate that problem.

I almost hesitate to mention it, but feel that I should. Some members (not all) have apparently had less than satisfactory experiences with Accel replacement injectors. There is a rather heated thread clogging up the TPI board with this topic, and you can read it for yourself and formulate your own opinion. It might just be something to remember in case you have similar problems in the next few thousand miles.

 

Thanks. Yes I am aware of people having problems with Accel injectors. I don't know all the details, but I have heard of this. I bought a set of 24 lb injectors for my 5.7L Formula about one year ago and have not had problems. Of course I only drive that car on weekends so I havent' put a lot of miles on it. I decided to take a chance on this car because of the price. The OEM injectors are lik $70 each, so that's$420 for 6, these were $200 shipped. Well I suppose you get what you pay for. Im keeping my fingers crossed.

 

got the injectors, put them in (coil replaced too). Fired up ok and seemed to run fine. My son went for a drive. He came back and it was running bad, kind of missing and dying. He said it died at every stop sign. Not doing the losing power when giving it gas thing like before tho. I tried to start it and it would not start without giving it gas. Gave some gas but it ran rough and died when letting off on accelerator. Started it a little later and got it running without foot on gas, disconnect EST and check timing, OK, 10 deg, . After that it ran good. Took it for a drive a little later and it ran perfect, started without giving gas, idled perfectly, didnt die at any stop sign, seemed to have good pickup, spun the tires at a stop sign.

What thuu????

 

after replacing the injectors, the car still had a problem. I had a diagnostic run at a mechanic and they said the fuel pump was bad. Change the fule pump, ran ok for a day, screwed up again, same way. INtermittent problem, loses power when giving gas and will die. Replaced the ECM, no more problem. This is what thought it was in the beginning.
summarizing, replaced more or less in this order

cap, rotor
plugs, wires
PCV valve
Fuel filter
Set timing
O2 sensor
ICM, twice (the first one was bad, got credit towards AC Delco no the second one)
Throttle position sensor
Idle air control
Injectors
Fuel Pump and strainer
Muffler (damaged it getting it off for fuel pump replacement
ECM

Whew!. Well at least I know we got good parts on the car. Im thinking about keeping it now, paint, interior etc. It would look awesome fixed up

 

Your old injectors may have done some damage to the ECM switching transistor. They may have started or contribited to the demise of your ECM.

Good luck with it. At least you now have a handle on some of the major maintenance items.