zsmoore68w

First of all, this is my first post on thirdgen's message boards, so I'd like to say hello to everyone! I'm a college student and a medic in Georgia's Army National Guard. I just bought my first Camaro, a 1991 Z28 5.7L TPI, a few weeks ago. The guy I bought it from told me he bought it with the intent to restore it, but after it sat around for over a year he decided he needed the money more than a lawn ornament. It's mostly stock, with the exception of a B&M Megashifter and a Pioneer CD player.
Now, my problems. Since I bought it, there has been a notable rough idle and more recently stalling randomly. I seafoamed it, then changed spark plugs, oil, oil filter, air filters, and pulled the idle air control valve and cleaned it to see if that would fix the problem but it only made things slightly better. I had to drive it two hours home from where I bought it, and it made the drive, although it did die a couple of times at 50-65mph. It seems that it runs fine when started cold, but as it warms up it begins to progressively get worse until the point that I'm afraid it's going to die any time I stop at a light. The idle bogs horribly when I'm braking to stop at a light, and gets a little better again when I shift into park or neutral. It's fine when I stand on the gas, for awhile anyways. After I give it a lot of gas and then let it coast, it sometimes stalls out for a couple of seconds, then fires back up before I have a chance to pull over and turn the key off and back on again. I took the car to a mechanic recommended by someone my girlfriend's mom worked with, and they did almost nothing even though I left my car with them nearly 5 days. I gave them as much information as I possibly could, suggested a few places to check, like vacuum leaks, fuel filter, fuel pump, distributor, airflow sensor, injectors, etc. and all they came up with was that my intake manifold gasket needed replacing. So the day I went to pick it up (after a week without anything to drive) they tell me that someone is doing a final timing check and that the car is "running much better" and thank me for my patience and all that bs. I go out to talk to the guy who is checking my timing, just to ask him what's up and how the car is and he tells me "Yeah um, I don't really know why but the fifth cylinder is skipping a bit, and when I was checking the timing it bit me!" Well, I'm all out of patience at this point, so I just attempt a smile and tell him thanks for his time, take my keys and my car, and leave. It only took a day or two for the rough idling to come back. Now it's almost as bad as it was before. I don't have almost no tools and very little money so I might be buying parts and taking the car to the nearby tech school to let their automotive department install them and perform whatever other fine-tuning needs to be done. Any suggestions would be greatly appreciated. Thanks!

zsmoore68w

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I noticed today when I was having trouble with the car again that my oil pressure gauge kept dropping when my idle was bogging. Also, the exhaust has a really strong, rich smell. And my radiator overflow level keeps falling, so I'm guessing there's a small leak somewhere, and I'm really hoping that small leak isn't at the head gasket. Once again, anyone's input is appreciated.

'87IROCZOWNER69

iTrader: (1)

I would start by running codes on it. I will now tell you how to run codes on your car.
You need:
check engine light needs to be functional
paperclip
notebook
pencil

After you have made sure that the engine light is functional you need to find the little 12 pin connector thats underneath the dash just below the check engine light. You then need to take your paperclip and form it so that you can fit the 2 ends of the paperclip into the 2 upper right holes on the connector. Once you have it put in you need to turn the ignition on without turning the engine on (turn to the point to just before it starts) I repeat DONT START THE ENGINE. Once you do that you should hear the fans kick on (I think thats what the sound is) and the check engine light will start flashing. It will flash a code 12 which will be a flash with a long pause and then two more flashes with short pauses between (also known as a long flash and two short flashes). After it flashes this code 3 times it will then start flashing your other codes (if there are none it will flash the code 12 again). Write down each code that flashes, once again it will flash each code 3 times before moving on to the next code. So, if you have a code 32 it will do 3 long flashes and 2 short ones.

After you get all the codes written down (when its done flashing codes it will follow up with the code 12 again at which point you can turn off the car and be done) come and type them on here so that we can decypher what each one is for you. I would also reccomend that you buy a Chilton manual as it lays out how to fix different things on your car.
Good luck!

zsmoore68w

the only code it was throwing was 12. flash, pause, flash, flash, pause, pause.

zsmoore68w

noticed air bubbles in my coolant reservoir while checking my trans fluid today.

blbruegg

This sounds to me like the module inside the distributor. Especially when they get warm they tend to do funny things like stalling. The bubbles in your radiator I wouldn't worry about too much unless you start overheating or finding things like moisture on your dipstick. sometimes when the thermostat opens it pushes a relatively large amount of coolant through the stock 1 core radiators and seems to cause some bubbling.

You can get a stock one from just about any auto parts store for around 40-45 bucks

You can also get the accel one from summit
http://www.summitracing.com/parts/ACC-35370/

zsmoore68w

started my car today to drive up to autozone to buy distributor cap, rotor, and ICM and it sputtered and died. never happened like this before. i popped the hood, looked around, and then started the car again and immediately noticed what sounded like a huge vacuum leak. the car died again before i got a chance to figure out where it was coming from so i turned the key off then pulled the airbox off to get a look at the throttle body and started the car one last time. i'm 99% sure it's coming from the hole at the bottom of the throttle body (i think to the IAC valve?) and it's loud. anyone know what to do for this?

'87IROCZOWNER69

iTrader: (1)

Hmm, I dont know if IAC valves have gaskets but either it could be the gasket or it managed to come loose. That's where I would start, and while you have the plenum off I would also check the EGR to see if that hasnt ruptured or has a bad gasket.

'87IROCZOWNER69

iTrader: (1)

Another thing, before you ran codes did you drive the car around? Because if you run codes right after you unhook the battery and dont drive it then the car will only flash code 12. If you did that you should now try running codes again.

LoganKello

did the previous owner replace the plugs or wires? My 91 Trans am would cut out on me when it was under load or going up a hill and the rpm's would bog and then jump and then bog and on and on. It was a simple spark plug change for me...just an idea if you dont find a soloution. other possible reasons for bogging/choppy would be fuel pump or distributor also. Hope you figure it out and welcome

(also at idle when it was humid out, it would sound like I had a real nice cam it was so choppy haha that was fixed also with the spark plug change)

And about the mechanic, I hate it when that happens, first off were payin anywhere from $90-$120 AN HOUR for a shop fee! And yet some still seem to do nothing even though you get billed $500 dollars.

zsmoore68w

i pulled the throttle body out and broke it down to check it out. looks like i've got a bad IAC valve and the gasket between the IAC valve housing and the throttle body looked pretty bad too, so i'm guessing that's where i had vacuum leaking. i knew it was coming from somewhere in there because the little hole in the throttle body that flows to the IAC was where the huge sucking sound was coming from, and the engine seemed to act right when i plugged the hole with my finger. so i'm ordering a new IAC valve and a few gaskets and hopefully when i get them installed everything will be okay. i also installed my new distributor cap and rotor and started installing my new plug wires when i realized that my floor jack and jack stands were at my mom's house with my old car and there's no way to get to all of the spark plugs without getting under the car. oh, also, what would be the appropriate stuff to use for cleaning my throttle body?

zsmoore68w

alright so i got the fuel pump replaced and working correctly, but there is still a problem with the car after it warms up. there's definitely something wrong with the air/fuel mixture because the exhaust smells rich, but i can't figure out the cause. ruled out bad O2 sensor. other than that, i'm completely stumped. and incredibly frustrated.

lunaticinaZ

Get a volt meter and check the voltage on the throttle position sensor. It could be going crazy when it gets hot and either giving a false reading of WOT or the throttle not open at all

danziger

I didn't see injectors mentioned, but if they are going it could cause the problems you have. Especially as they warm up...

ASE doc

First clue to trouble is the mechanic getting "bitten" while setting the timing. You need to start with the basics. The wires are probably original which puts them at 20 years old. They were good for 60,000 miles or three years so they need to be replaced, along with cap and rotor.

Second clue is bubbling in the coolant reservoir. This is symptomatic of a failed head gasket. If the bubbling is constant once the engine has reached normal operating temp, you will need to replace head gaskets. If you want to try doing just one, you can look at plugs for a clue as to which hole the gasket is blown on. That plug will be cleaner than the others.

Once you've done that, you may need to check injectors. These TPIs are hard on injectors because of heat. Once your basic tune is good, head gaskets are sealed, and you've verified that the injectors are sound, should the engine still not perform as it should, I would suggest connecting a scan tool to look at data for clues.

The noise at the throttle body is normal. These are port injected engines, meaning that the intake is dry. That makes for very loud, dry air rushing through the throttle body and the IAC port.

tigeraly

I had the same problem with my 86 z28, rough idle and stalling. I had to replace the mass air flow sensor, throttle position sensor, and have it timed to clear up the problem. runs smooth now and no stalling

ASE doc

I forgot to mention spark plugs along with wires, cap and rotor. MAF could be the cause and so could TPS. Scan data would show that.

zsmoore68w

finally got it checked out. found that my #8 injector that was shorting out and messing up the rest of the firing order. unplugged that injector and the car runs a thousand times better as a V7 lol. however, obviously it doesn't run perfectly. probably going to go ahead and replace all 8 injectors. there is another thing that's bothering me though. even though it runs fine most of the time as it is with 7 injectors, once i've driven it around for awhile and got it nice and hot, it starts to act sketchy again just like it does when i have the bad injector connected. anyone have anymore advice here?

theNMBR27

90-92 is speed density so no MAF. I replaced my injectors with Ford blue tops when they crapped otherwise I hear good things about southbay.

Acting up when hot is a sign of failing injectors. If you want to test them grab you digital volt meter and set it to 2000 ohms, you should have a resistance of 16 ohms with a variance of .5 being ok between them all. Check them cold and then when the car has reached operating temp. Three of mine were 3, 5, 2 ohms while all the others were 16.2.

zsmoore68w

yeah i ordered a set of bosch iii's from southbay. other than that i noticed my oil pressure drops whenever it starts to die, and that when it dies it acts like is running out of gas, and my mechanic told me that he got a few low fuel pressure readings when he was checking it out, so i ordered a high volume oil pump, a water pump, and a fuel pressure regulator. on top of that i ordered a jet stage 1 chip and a jet 180 deg thermostat, as well as a new pcv valve and fuel filter. the only gauge that works all the time is my oil pressure gauge, and the speedo works when it wants, so i'm trying to find a gauge cluster somewhere. oh and the injectors i got are 24#, so i'm probably going to need to change that chip's settings a little won't i?

theNMBR27

The jet chip is worthless you're better off getting a custom burned chip since you have to change the injector size

Patrick Day

Have you checked your EGR valve?

zsmoore68w

i did replace the EGR valve. and i kind of just got fed up with searching for someone who burns chips so i just went ahead and got a jet chip for $100.

RBob

iTrader: (1)

Classic case of the shorting Multec injector coils. As they heat up the others are starting to short out. Good deal on getting the reman Bosch from South Bay.

The lower oil pressure as the engine starts to die is normal. The HV oil pump is not required.

RBob.

zsmoore68w

thanks for the heads-up bob!

MrPink

iTrader: (6)

I would try these 3 easy things. 1) Set Minimum Air correctly. 2) Replace MAP ($40). If those don't work 3) Replace ECM. That fixed my idle problems (for the most part).

Fred SS

iTrader: (3)

zsmoore68w, I know this is an old post, were you successful at getting your car to run smoothly?

Redrallysport

I know this post is old but if you are still having trouble with it I suggest you clean your Cadillac converter mine kept stalling and once I cleaned the cat it hasn't stalled since

dereklicon

wow resurrecting a 3 year old thread?

I had the same issues and replaced everything, (TPI 305) it ended up being a blown head gasket between cyl. #4 and #6.

Good luck everyone

gregmy123

See next post.

gregmy123

Re: 91 5.7L TPI rough idle and occasional stall
Quote:
Originally Posted by zsmoore68w View Post
yeah i ordered a set of bosch iii's from southbay. other than that i noticed my oil pressure drops whenever it starts to die, and that when it dies it acts like is running out of gas, and my mechanic told me that he got a few low fuel pressure readings when he was checking it out, so i ordered a high volume oil pump, a water pump, and a fuel pressure regulator. on top of that i ordered a jet stage 1 chip and a jet 180 deg thermostat, as well as a new pcv valve and fuel filter. the only gauge that works all the time is my oil pressure gauge, and the speedo works when it wants, so i'm trying to find a gauge cluster somewhere. oh and the injectors i got are 24#, so i'm probably going to need to change that chip's settings a little won't i?

In your initial post you mentioned you had very little money yet you bought and installed: a Fuel Pump, EGR Valve, High Volume Oil Pump, IAC Valve, 8 Fuel Injectors,Water Pump, Fuel Pressure Regulator,a jet stage 1 chip and a jet 180 deg thermostat, distributor cap, rotor, and ICM. How much did all of this cost you? You just replaced everything you could and did not really take too much advice from members. On the Fuel Pump/Filter- did you test the pressure at the rail? No, you just replaced the pump/filter. Great Job.