Car cuts out

I have a 1991 Camaro V6 3.1 MFI. It will cut out when ideling if ran long enough or if you rev it, it will cut out. I have replace the spark plugs and wires, cap and rotor. also fuel filter and the fuel pump. and nothing seems to be helping. I am starting to lean towards a sensor now. But I am not sure which, or if there is anything else it could be. Does anyone have any ideas?

I would take a look at the TPS (throttle position sensor)

I dont think that is it because for one there sould be a code for it when the circuit is not working and second the ECM sets a default value for it when it does go so you can still drive it eventough it will run like shit

crank sensor?

there isnt one on it

I dont think that is it because for one there sould be a code for it

key words "should be".

Well I tested it anyway and everything was ok with it except for the ohm at high throtal it dropes a bit but that cant be the problem because I am having the problem at idealing.

Do anyone have any ideas?

IF i am thnking correctly, testing resistance is reverse of voltage, and the dead spot is at idle.

What are you talking about it is not at idel it is a full throatle I know this because my hand was holding it open

Yes, WOT would be max voltage, which in turn should be minimal resistance (ohms)

Just trying to help you out.

sorry if I came off like an ass didnt mean it like that

No problem :thumbsup:

So when it 'cuts out', does it fire right back up with no problem?

No other running / driveability issues?

yeah it starts right back up

yeah it starts right back up

Okay, so that pretty much elimnates the famed ignition control mod problem and other ignition related symptoms.

I'm telling ya, it sounds as if the ECM is losing sight of where the throttle or air/fuel ratio is at for a split second and sending it into a fit. Since you've confirmed you do have a dead spot in the TPS, there's a problem already, they're relatively cheap, I'd replace it, and reset the ECM and see how it does.

Believe me, I am definately not one to 'shotgun ' parts, i'm a get it done right the first time. There are a few other things possible to cause this, but you know it has a problem in it, so at the very least it will be eliminated from the picture. Yes, i usnderstand your logic that performance wise, where the spot is located should logicly cause a loss of reference at a open throttle situation, but the overall resistance of the circuit could be lessened, thus creating a 'out of range reference voltage in the TPS circuit'. And as stated before, on GM OBDI systems, it's not too uncommon it will not throw a hard code to set off the CEL.

I replaced the TPS now and it was doing the same thing. How would I reset the ECM? is it a simple as leaving the battery off?

Yep disconnect he bettery. Damn, I was fairly confident .

Yeah I disconected the battery and still does the same

Alright, back to square root one.

You bought the car not too long ago. You had posted up a question about where the fuel filter was at. Same issue?

All the other times listed in the first post of this thread also as a result?

yeah same issue

All the other times listed in the first post of this thread also as a result?


I dont get what you ask here

Sorry,

I'm trying to keep up with my notes on this one

So we have a 91 3.1, "that stalls at idle or when revved" and after stalling, "starts right back up".

Replaced thus far:
-plugs/wires/cap & rotor
-fuel pump and filter
-TPS

So, other than the TPS that we know of, were the ignition and fule system itmes replaced in attempt to correct the stalling problem?

Yes that is all correct and yes everthing I did was after the problem

just to refresh your memory

It runs for about 5 seconds and then sputters and dies like it is orunning out of gas

I replaced the pump and the filter so I know thats not it but now I am thinking it is the pressure regulator but I dont know if the fuel line goes to the nipple for the pressure tester or does it go to the pressure regulator first?

You mean to put a gauege on it? There's a schrader valve on the fuel rail you hook up to. The old fashioned, vacuum/fuel gauge will not work in this scinerio. Could be a sticky diaphragm in the regulator. Check the vacuum hose on the regulator for gas.

That was a big help saying it sputters. :)

Otherwise, when it runs, it runs normal? Meaning normal RPM.

yeah I know how to check it but I wanted to know if the pressure I am getting is after the fuel goes through the pressure regulator or not

The entire system runs the same pressure from the pump to the regulator.

yeah but when I do a pressure test am I testing it after it goes through the regulator of before it goes into the regulator

Before

So it is a good possiblity that the regulator is messing up the pressure?

If what you said in this thread is still the case and that when the engine stalls the PSI drops from 40, yes.

http://www.automotiveforums.com/vbulletin/showthread.php?t=886743

no, it is at 40psi and when it cuts it stays at 40 like it should

It not the ECM I replaced it and it still doers the same thing, ther was water in the tank but I got that out and it runs a little better and longer now but still cuts out and I get the 33 and 35 code one is for the IAC valve and the other is for the map sensor.

I tested the map sensor and that is good

How do you test the IAC valve

How do you test the IAC valve
The IAC is a stepper motor, the only way to test it is to ohm out the windings. While you have the ohm meter out, ohm your injectors. They should be 15-17 ohms BUT there should be no more than 0.5 ohms difference between any of them. Check them cold, then try to get the engine warmed up good and check them again.

alright will do

check your injectors. im not 100% sure of what the resistance should be, but the V8 injectors are 16-17 ohms. but the important thing is that all the injectors have the same resistance.

the problems your having sound very similar to problems i had with my IROC, except my car wouldnt start right up again after stalling. Checking your injector resistance is easy, and dosnt cost anything. id give it a shot. seems like youve covered most of your other bases pretty well.

check your injectors. im not 100% sure of what the resistance should be, but the V8 injectors are 16-17 ohms. but the important thing is that all the injectors have the same resistance.

the problems your having sound very similar to problems i had with my IROC, except my car wouldnt start right up again after stalling. Checking your injector resistance is easy, and dosnt cost anything. id give it a shot. seems like youve covered most of your other bases pretty well.

From my understanding wouldnt the injector failing create a missfire not make the car cut out

From my understanding wouldnt the injector failing create a missfire not make the car cut out

not necessarily. I had a similar issue with a 90 cutlass 3.1. it would start up and run fine, then once it got warm it would cut off. ended up having 3 bad injectors. it didn't set any codes though. it's worth looking into like 89 suggested.

yeah I guess 3 bad injectors would do that so when I do the test does the car need to run for this and can this be seen with a nod light

http://www.asashop.org/autoinc/june98/techtotech.htm

Fuel Injection Service, Not Just Cleaning

By Jim Linder

After many years of fuel injection "service," I think that some service technicians still misunderstand the process of proper fuel system handling. Much has been said over the years in regard to when and how to perform injector cleaning. Some manufacturers have suggested methods of cleaning while others have issued bulletins to disregard any cleaning at all.

For this reason, I offer the following suggestions on the proper process for injector service on today's vehicles.

To begin, all engines using fuel injection do in fact require some slightly different fuel system maintenance! The normal wear and tear with today's underhood temperatures and changes in gasoline quality suggests some buildup of olefin wax, dirt, water and many other additives. Unique to each engine is an air control design that also may suggest different levels of carbon deposits, such as oil control or just the location of the component or control device itself.

To simplify the approach, I will use the word "service" since the phrase "injector cleaning" is misleading as to the real function needed to maintain the vehicles of today!

Fuel Injetor System Service
(Note the words "system" and "service" in the subtitle, and not "cleaning!")

The proper steps in fuel injector system service are:

Check fuel pump operating pressure and volume.
Test pressure regulator for operation and leakage.
Flush entire fuel rail and upper fuel injector screens to include pressure regulator.
Clean fuel injectors.
Decarbon engine assembly.
Clean throttle plate and idle air control (IAC) passages.
Check minimum air flow rate and adjust if needed.
Relearn onboard computer.
All eight steps may be performed using one of the "two-line" fuel injector service units. (Carbon Clean, Injector Test, DeCarbon and Motor-Vac, to name a few.)

Check fuel pump operating pressure and volume
The missing link here is volume, as most working technicians assume that if the pressure is correct, the volume is OK also! By hooking up a fuel pressure tester to the fuel rail inlet and return, and using the pressure side feed t-Ed into the fuel unit, we can quickly test the fuel pressure with engine running but also at the same time test the volume of the pump by stealing fuel into our holding tank (one pint in 30 seconds is the usual specification). When proper volume is flowed into the tank, we would shut down the engine and change hose connections to allow the machine to be put in control of the fuel supply system. The two line system would be attached to inlet and return on the fuel rail, with the vehicle's onboard system being "looped" and returning fuel to the tank. This prevents disabling of the factory unit.

Test pressure regulator for operation and leakage
At this time, the regulator would be tested for operational pressure and proper regulation including leakage. (This works well as the operator has total control of rail pressure with the unit control valve.)

Points to Ponder:


Good pressure doesn't mean proper volume! Example: A clogged filter may test OK on pressure, but restriction may not allow proper volume under load!
There is some logic to using the vehicle's gasoline to service the system as opposed to a can of shop gasoline that has been around for some time!
Pressure regulators do fail and a lot more of them don't properly shut off the fuel, causing higher-than-normal pump wear and shorter life!
Flush entire fuel rail and upper fuel injector screens to include pressure regulator
At this time, I would suggest raising the input pressure to a point above the regulator setting to allow a constant flow of fuel through the inlet pressure side of the system - through the fuel rail and out the open fuel pressure regulator. In most cases, the apply pressure is 75 psi to 90 psi but will be maintained by the presence of a regulator. At this point, a cleaning chemical is added to the fuel mixture at a 5-1 mixture and allowed to flow through the system for 15 minutes to 30 minutes. (I have some GM dealers that use one hour per vehicle with great re-sults!) Results are best on a hot engine, and fuel supply is looped with the vehicle's engine not running.

Points to Ponder:


This flush is the "fix" that most vehicles needed to begin. The difference is that you are effectively removing the deposits to a remote tank and filter vs. attempting to soften and blow through the upper screens.
Most injectors use a 10 micron final screen.
A 25 percent restriction in the upper screen would increase the injector on-time approximately 25 percent!
Injectors have a working "duty cycle" like a welder. Extending the duty cycle equals a shortened life of the coil or bobbin.
Each engine has a "pattern failure" in the system. Example: Buick V-6 engines have problem injectors on the rail curves and the injector next to the exhaust gas recirculation (EGR) valve. Those three injectors will always show a restriction to flow first! Cylinder No. 5 is the pattern failure on 4.9L Ford in-line 6s. (Study the rail design and look for the problem areas.)
Clean fuel injectors
At this point in the "service," we start the engine and adjust the output pressure somewhat closer to regulator pressure or somewhat lower. Adjusting lower will cause the pulse width to open up somewhat longer and allow the injectors to be cleaned. Slow speed (idle) position will take a longer time frame and operating temperature will be reached. This is one place where time is required. Did you ever wonder how a can of injector cleaner could clean the entire injectors in nine minutes? (It can't!) Remember, not only do we want clean injectors, but we also want the chemical to decarbon the engine valves, pistons and O2 sensor.

Points to Ponder:


Time is required to perform this service.
Internal pintle cleaning is performed during this cycle.
Fuel control is always in direct response to O2 response. Example: Slow O2 = slow fuel control = poor performance.
Decarbon engine assembly
On most vehicles, the injector spray is going to help the decarboning process. On others, we may need to enhance the operation with an external addition of mixture through PCV hoses, throttle plates or idle air controls.

Points to Ponder:


Most technicians (especially very young ones) think carbon is a 1990s problem. The older guys (especially the very old ones) remember throwing rice through a flathead at 2500 rpm and watching the black specs fly out of the exhaust. This is still a problem in the '90s (although rice is not suggested). We have a lower fuel volatility, and in some cases too high of a compression may cause a no-start situation.
Proper compression = 14.6 x compression ratio.
Clean throttle plate and idle air control passages
Just this "service" alone on most late model engines will show a manifold vacuum increase of up to two. You may stop the engine and clean the areas as needed, but my suggestion is to use an extra hand-held fuel injector hooked in parallel with the pressure hose along with a pulser to allow a cleaning of throttle plates with the same chemical as the injectors are running on. This has proven to work very well as air drawn into IAC passages on a running engine will clean the passages without IAC removal. Neat trick!

Points to Ponder:


A manifold vacuum increase tells the technician that the engine "liked" the service.
Using the hand-held injector usually will lower a General Motors IAC count from 40 to 15 without touching a thing! (Think about this.)
Check minimum air flow rate and adjust if needed
Most vehicles' "stall" problems are due to a misadjusted throttle plate or incorrect minimum air rate. Check service manuals for specs.

Points to Ponder


ACDelco makes a set of small "tuneup" booklets that do an excellent job of covering minimum air rate adjustment procedures.
Relearn the vehicle's onboard computer
Some vehicles may have been running in such a poor state of operation that the onboard computer may need to be relearned! Consult the OEM-suggested relearn procedures per make.

Fuel injection system service is complete! This "service" usually takes approximately one hour for the vehicle to run out of fuel and the entire service to be performed. The good thing is that the technician may do other services while this is being performed! Some of my customers put in a set of plugs while the engine is flushing or change the fuel filter or do the brakes. Charges are up to the individual shop, but the performance gained is absolutely amazing.

In reality, all you are doing is exactly what should be done with mileage, and that is restoring the system to original operations.

http://www.thepartsbin.com/fuel-injectors.html

Do Your Fuel Injectors Need Replacing?
Failed fuel injectors can be a cause for a great many problems with your cars overall performance. Whether your car has an electronic fuel injection system (E.F.I.) or a constant injection system (C.I.S.) the problems experienced from both are very similar. Here are a list of some of the symptoms you may be having caused by poor fuel distribution by faulty fuel injectors.

(1 Hard Starting
(2 Poor fuel economy
(3 Rough Idle
(4 Car runs fine when cold and terrible when warm
(5 Car will start just fine when cold and not when warm
(6 Getting a fuel smell inside the car
(7 Loss of power in acceleration
(8 Fuel leaking from injector seals or injector

Injectors are just as easy to replace as your spark plugs.

In either system fuel injectors should be replaced every 80,000 to 100,000 miles as a regular maintenance part. Some professionals insist on replacing them and part of a major tune up at about 90,000 miles. The reason for this is that the internal mechanics such as the springs, needle seats, and plungers start to weaken and will not allow the fuel injector to open and close properly. By not opening and closing properly the injector will send too much or too little fuel to the engine causing it to flood itself or starve itself for fuel resulting in the problems listed above. Remember to change all the seals, orings, and holders required with replacing injectors.

Think You Can Just Clean Fuel Injectors...

Most fuel injectors can be cleaned for a while but eventually the constant movement of the internal parts causes the fuel injector to just wear out. Cleaning will not solve this problem. However using a better fuel will always help to keep the injectors clean which will make the injector perform better and longer. Faulty fuel injectors if not replaced can also cause damage to other fuel system parts such as fuel filters, fuel pumps, check valves, fuel regulators, and fuel distributors. This could cause hundreds of dollars in additional repairs. Keep your car on the road longer by replacing your fuel injectors regularly

From my understanding wouldnt the injector failing create a missfire not make the car cut out

it will have a missfire while running, my IROC has a slight misfire, that i didnt think was very serious, the car had been sitting for a while, had old gas, dirty spark plugs, etc. etc. and i didnt think anything of it cuz it still ran like a rabbit with its butt on fire. then when i went to get it inspected after it was warmed up, i had a problem getting it started after i cut it off, and noticed a hunting idle, and a few other problems. but it only did it when warmed up. i wound up replacing spark plugs, cap, rotor, wires, ignition control module, setting the timing more times than i can count (somewhere around 12 :icon16: ) and then doing a google search was reminded about injectors. im pretty sure the ones in there are the originals at 150k miles, so i checked em. 7 are at 17 ohms, and the number 5 cylinder came up at 2.3 ohms. i unplugged that one injector, and she fired right up with no muss, no fuss. and thats how she's sitting in the driveway right now till i get home in may to replace all 8 injectors.