I recently purchased a 1988 Camaro for my wife. The car is in excellent condition in all aspects except for the way the motor idles.

It idles extremely rough and stalls frequently either in park or when I'm coming to a stop at a red light.

I have replaced the following components:

EGR valve

TPS ----------adjusted voltage accordingly

Oxy sensor-------------I don't think that this is the problem since it runs rough in both closed and open loop.

IAC -------------Again, I adjusted according to instructions

MAF sensor

checked for vacuume leaks found a couple of dry-rotted lines and replaced accordingly..............

The only sensors I didn't replace yet are the CTS, Egr solenoid, and the MAT sensor.
I am getting a code 32 and 24 intermittenly. even after changing the EGR valve but something tells me that this isn't the problem with the idle.
Could a cruded up fuel injector cause a profuse idling problem without making it run bad while driving? The car runs great on the open road and it starts with no problem.
The person that I purchased the car from said it's not the original motor. I didn't see any disconnected wires or anything out of the ordinary.
Any suggestions will be appreciated.

 

Code 24 is the vehicle speed sensor. Im sure the error is probably a lack of signal to the ecm so it shouldnt do much idle wise. Check the vacuum to the egr valve when the car is idling. There should be no vacuum at the line thta feeds the egr valve. Your symptoms sound like a classic egr problem. Runs great untill the car has to idle.

 

Unplugging the vacuume line was the first thing that I tried after I installed the new EGR valve. There was no change in the way the engine idled. The original EGR valve didn't look too carboned up ,but I replaced it anyway.

Something tells me that I have an injector that's not spraying correctly. I just don't want to start ripping off the plenum and fuel rails if I don't have to, it's just too damn cold outside.

 

Can you get a fuel pressure reading?

 

Actually, I didn't get to that part of the system yet. I'm assuming that the replacement motor in that car probably sat for a while where ever the previous owner got it from , so there's a distinct possibility that the injectors might be either cruddy or defective.
Just out of curuiosity, could a CTS cause this problem in all ranges of closed and open loop? Also, when I pulled out the old O2 sensor , it was carboned up pretty bad so I'm assuming that the fuel to air mixture is not correct.

What is the cost of mpfi injectors thses days? If they do turn out to be screwed-up I'd rather replace all of them instead of playing games tearing off the upper plenum by trial and error.

 

Get a fuel pressure reading like vader said. A bad CTS could also be a contributing factor as well since the fuel/air ratios would be off but if its going into closed loop, then the cts is at least in part working.

 

Could a CTS be defective even though it doesn't cause the ECM to throw a code?

The way the exhaust is burning my eyes and by the amount of carbon residue built up on the old O2 sensor , I know that it's running way too rich.
I'll have to see about obtaining a fuel pressure gauge.

What is the procedure with checking if the fuel pressure and injectors for abnormalities?
Is there a sequence of steps that I should take?
Any help would be appreciated.

 

After all the stuff you replaced, did you reset the computer? Just making sure you're not working off an old code.

 

I sure did, several times as a matter of fact. When I first bought the car the SES light came on. It had four trouble codes stored in it. I figured that the person who installed the motor forgot to clear out the ECM.

The codes were :

34

22

24

32

I got rid of all of them except the 32 . I replaced the EGR valve and gasket, it really didn't look too bad to begin with. I didn't replace the EGR solenoid because something tells me that this isn't whats causing the erradic idling. I have a hunch that it's in the fuel delivery system.

 

If you want to get the CTS out of the equation, measure it cold with a DVM and it should give something like maybe 6-8 kOhms and with the engine hot itll be a couple of hundred ohms. Dont know exacly off the top of my head but if you get those values then its probably ok.

A fuel delivery problem would definatly cause problems. Possibly leaking injectors. Some of them can leak so bad that the car runs on without the ecm even hooked up. Id say vacuum problems possibly as well but with maf it would lean out the mixture. Any ignion problems to speak of?

Oh, the egr code may be because the egr port in the head is plugged up with carbon deposits and teh egr no longer functions.

 

I already checked for vacuume leaks . I replaced the MAF sensor , no change occured.

The CTS sensor is next on my replacment list. After that I will start on the fuel injectors and related components.
Is here any way that I can clean them myself if they are crudded up? I know that they are delicate and there are certain solvents that will destroy them, but I think that I can handle any maintainence in regards to cleaning them.

I just need to know the do's and don'ts. I'm used to working on carburuators [sp] , mpfi's are sort of new to me. I just don't want to make any fatal mistakes.

 

It stalls when your in park or when you're coming to a stop.
You get EGR and VSS flags still.

I think you may have replaced a good EGR and you should swap out your bad VSS. The VSS input, IIRC, helps in the controls of the TPS, IAC and some other stuff. Try there first is my penny. I would also invet in a set of MAF relays with a new MAF, cheap insurance and it will get one other thing out of the equation, although when they usually go it is <i>generally</i> apparent by the car stalling right after starting.

And unless you're running really rich (again generally speaking here) it's not going to be the CTS. TPI was made to be lean and will run rich as he*l so unless you have no pressure or your temps are shooting up fast or your headers are glowing or you're shooting gass out the tailpipes I wouldn't worry over the CTS.

 

I haven't been under this vehicle in any detail with the exception of changing the O2 sensor. Where exactly is the VSS located? I read in the Haynes that the VSS could cause this problem but I was a little skeptical especially when the problem is on a vehicle that's not in motion. I figured the VSS is only working when the car is moving. Apparently I was in error.Is this component a dealer only item or can it be obtained at a local auto parts store?

 

The VSS will be on the rear of the speedo in the instrument cluster. Didnt think lack of pulses from the VSS would cause problems as the computer would think the car would be at rest without the pulses but its entirely possible that it can cause problems. Red Devel might be onto something. Try replacing it and see if it helps.

 

Well I spoke to a mechanic friend of mine who told me that the underside of the throttle body can get crudded up to the point where it's restricting minimal air flow. He says that this engine is notorious for this problem.

I'm still going to change the VSS and I'm also going to rip off the Throttle body assy and clean it out with carb cleaner. I hope this works because I'm starting to get a brain tumor over this idle problem.

Whatever happened to the good old days when all you had to do was a simple tune-up and a timing and carb adjustment?

 

I have an '86 2.8, and had the exact same problem. Replaced everything you did (which did contribute to the problem) but still did not fix the stalling during stops and hesitation on acceleration. In my case it was the fuel pump. Did not assume that was problem, until it died one day. After replacing it the car ran great.

 

I just found out today that it might be the fuel pressure reg. I was instructed to remove the vacuume line off the regulator while the motor was running and see if there was a change in the way the motor idled . He said that if the reg. was bad, there wouldn't be any change in the idle.

I did this and there was no change at all. Actually , with the vacuume line off it idled better [smoother].
This car is running way too rich, the old oxy sensor was caked up with carbon soot. The throttle plate was also loaded up with carbon.

I'm going to buy a new reg. tomorrow. I have to find out the procedure on how to remove it. The Haynes book doesn't go into detail on how to do this. They said it's a permanent part of the fuel rail and it cannot be serviced. If that's the case, then how does one replace it?

Any suggestions?

 

Before you condemn the regulator, you really should test the fuel pressure with a reliable guage.

 

I did, there's 42lbs of pressure when I turn the key on and while it's running.

All sensors have been replaced. I was informed by the previous owner that a new timing chain and gears were put in. It doesn't run rich anymore since I changed the regulator and CTS, but it still lopes like there's a high performance cam in it. Power on the open road is terrific. I tried disconnecting the four wire connector in the distributor and the car stalled. I wonder if the person who put in the timing chain tried setting the timing with the EST wire connected.

What do you guys think?

Also, is there a special wrench that is needed to loosen the dist. hold down bracket. I have dist. wrenches that are bent at a 90* angle but it doesn't look like there's enough room to turn it.

 

If the idle got smoother when you removed the vacuum line from the regulator, then you are running slightly lean. With no vacuum, the regulator bumps the pressure up, making you run slightly richer.

As for the EGR code, next to the EGr there is a solinoid, that is activated by the computer, there is a vacuum line that is on the top that tees off and one line goes to the EGR valve itself, and the other goes to what looks like a MAP sensor mounted on the coil bracket close to the firewall. This sensor tells the computer that the solinoid is working.

When the computer cycles the solinoid, vacuum is diverted to the EGR valve and the sensor, the sensor then tells the computer that the system is "working properly." On our cars, there is no way for the computer to be able to tell if the EGRvalve itself is working or flowing, so many people forget that. You might have an intermittant problem with the solinoid, or maybe even the sensor. This could also be your idle problem. I don't know exactly how the computer responds to the EGR signal(does it make it run leaner by shortening pulse width, or richer by widening pulse width, I don't know). just something else you might want to have a look at.

 

If I'm not mistaken the EGR solenoid energizes the EGR valve during certain driving conditions, and since the EGR valve doesn't energize when the vehicle is idling I can't see how that would cause the car to idle erradically. I replaced the EGR valve just in case it was leaking past the needle and seat so I know that's not the problem, and besides, there's no vacuume at the valve during idle to energize it.

I am however throwing a code 32, not while the car is idling, but when I'm on the open road driving it for a few miles. The solenoid may possibly be defective , but I can't possibly see how that would affect my idle.

Something tells me the timing is off since I was informed the chain and gears were changed, possibly creating insufficent vacuume to operate the EGR valve. The car idles like it's got a high performance cam in it. It runs great on the highway but wants to stall when I come to a light . I will check this tomorrow.

 

Gunsmith,

You're correct about the EGR operation. A new valve that doesn't leak shouldn't be causing any idle problems. The EGR vacuum solenoid could be leaking, however, which may cause problems. If the EGR vacuum source is completely disconnected and capped, and the EGR valve itself is not leaking, you should look elsewhere. Other potential leaks are teh PCV, power brake booster, etc.

This may help a bit, too:

 

I just checked my timing. With ESC disconnected it was 20* BTDC .Too far advanced .I assume the normal timing is around 10-12 * BTDC.
After I checked the timing with the ESC plug disconnected I plugged it back in and there was no change in timing. Is this normal or is there something wrong with the distributor module?

I was always under the assumption that when you plug the ESC back in the timing should advance some. Or am I wrong?

 

Your assumption is correct. Once the EST takes control, timing should change dramatically. The system will test the KS by advancing the timing. Of course, none of this will happen in Backup Fuel and Spark Mode. Is the SES lamp ON while the engine is running?

 

Hadn't noticed the light only because I knew the light would come on when I unplugged the ESC .

I'm happy to report that most of my erradic idle has gone away. However, it still stumbles slightly. I was reading about the pick-up coil and the dist. module. Also when I manually throttle the motor from under the hood and hold it around 2000-2500rpm, it seems as though I'm getting an intermitten missfire. The plugs , wires, and cap were changed so I'm ruling them out as a possible problem. I was wondering if the dist. components could cause this "stumble" with my idle. Also, the tach is tweaking up and down when the car is idling.