Hello, I just found this site and thought I would see what you think is wrong with my 1988 IROC.
I just bought the car last week from a friend who was the original owner. I wasn't looking to buy a car but the offer was to good to refuse.

The car is a stock, clean and straight 1988, 305 TPI, 5 speed with 92,000 miles. It was well maintained, oil changed every 3,000 miles.

When the car is cold, it starts great (foot off the gas) after just a couple revolutions and gives a small puff of blue smoke (no biggie, valve guides or seals)

The problem is when I shut the engine off and try to restart it. The engine can be off for a minute or an hour but the only way it will start is with a wide open throttle. After it starts there is a large cloud of smoke that smells like gas. I then need to run the engine at 3000 rpm or so for a couple of minutes before I can drive or the engine will die.

The engine will warm up while idling but the temp will go almost to the bottom when driving. I asked the original owner about this and he said that he thought that the dealer may have removed the thermostat while it was under warranty because he didn't like the temperature going over 200 degrees.

When the engine is running the RPM usually runs at and will not drop below 1250 RPM and sometime goes as high as 2000 RPM.

If I floor the throttle while driving at 3000 rpm and above I get a noise that is hard to tell where it is coming from. It sounds a little like detonation, but I've also heard a loose baffle in a muffler make a simular noise. It is not the easily recognizable death rattle detonation sound.

Gas mileage is bad and power is down. Sixty miles drank a little over a half a tank.

I have a lot of experience with carburated engines but very little experience with computer controlled engines. The engine is solid no knocks, thuds or rattles.

I also need to know what code scanner I should get for this car. I see them range from $30-$300. Will a $300 dollar scanner tell me anymore about an 88 IROC than a $30 scanner?

Thank you in advance for any help.
Ken

 

Is the check engine light illuminated at any time?

Also, you're running extremely rich. You're getting way too much fuel for one reason or another. I'd do a fuel pressure and fuel volume test to see what kind of fuel you're getting up to the fuel rail.

After that you might pull your plugs and see if all of the plugs are fuel soaked or just a few of them. If one or two plugs are soaked in fuel but not all of them, you could have a bad ECM causing the injectors to spray WAY too much fuel.

Another thing that kind of concerns me is the fact that you said that it runs fine when it's cold. This tells me that in open loop the vehicle runs fine, which means the ECM is taking no measurements from any of the sensors. If you try and start it when it's warm though(in closed loop when the computer is taking measurements from the sensors) it runs like crap.

 

Ha! I had that problem with my 305, cept I knew exactly what it was.

The problem is the head gaskets, they were almost ruined but still basically intact. I made it a reliable car, but only one way. I fixed it with one application of sealer and proceeded to beat the **** out of it for the next 4,000 miles until I replaced the engine with a new 350. It seemed to hold together fine after the sealer, but replacing the gaskets would be the ultimate solution.

At least it sounds exactly like mine, probably the same problem. Check it out to make sure. Good luck.

 

might want to think about changing the O2 sensor. that's a common cause of mixture problems, and a cheap/easy replacement that many people ignore.
it's also not used in open loop. but i think the suggestions about checking fuel delivery are probably also good idea if this doesn't help.

 

Thank you for the replies.

The check engine light does not come on.

I plan to buy a fuel pressure gauge this weekend so I can check the pressure and see if the system drops it's pressure after shutting off the engine.

How do I do a fuel volume test?

I don't have a code scanner yet, but plan to buy one. Which scanner do you recommend for an 88 IROC? Will a $300 scanner do anymore on a 1988 car than a $30 scanner?

I don't think the head gaskets are bad on this car. The oil and water are clean and after the car is warm I get no steam from the exhaust.

Thank you for your help.
Ken

 

I heard that problems with warm restarts could be caused by leaky injectors.

 

tpi girl has a good idea. also another thing not to forget on TPI is the fuel pressure regulator. it could be ruptured and causing the problems you describe. let the engine run and then check the vacuum line coming from the FPR to the plenum. if it smells like or has liquid fuel, more than likely it's been leaking fuel being sucked into the plenum. that will cause a overly rich condition and will ruin the motor if not corrected.

 

it sounds like a problem with an old faulty sensor since the car runs great until it starts receiving feedback from the sensors ( closed loop) also sounds like you maybe have a leaking injector, should be pretty easy to tell, after you get your fuel pressure gauge see if the fuel rail will hold a constant pressure when not running or if it slowly bleeds down, if you get a slow or fast leak down its a injector(s) most likely, if thats the cause you may be able to pin point the injector by pulling the plugs and noting which one looks like its running pig rich.. as far as a can tool you could always go with the low cost GM OBD1 Generic Scan tool that can be purchused at your local staples or possibly found laying around the house possibly by a desk, this tool is better known as a paper clip and is extremely useful in pulling codes through counting the pulsations of the check engine light, for more info on this click the search button and type something along the lines of pulling codes, particularly a post by vader because he goes into great detail as to the exact procedure that will probably cost you nothing provided you can find a paper clip or a similar substitute. As far as your problem with the car running extremely cold, simply unbolt the thermostat housing and see if theres one in there, if not simply put one in, it sounds very much like the complete lack of a thermostat or a thermostat stuck in the open position.

 

thats EXACTLY what popped into my head too..


when you try to start with it at WOT, the computer assumes the engine is flooded, it stopps adding fuel, and the car starts with the fuel thats leaked in there...(and blows a lil rich cloud out the back)

 

Clear flood mode to be exact.

The only reason WHY the car starts fine when cold is that the fuel sitting in your combustion chamber has had time to evaporate a little. I don't supsect a sensor issue... but I'd change the o2 AFTER you cure the crazy amount of fuel you're dumping in right now...

 

Welcome to ThirdGen.org!

As for the code scanner, most of us have the best success with the GM OBD-I Diagnostic Trouble Code (DTC) Retrieval Tool. However, most people know that more commonly as a "paper clip". I suppose you could also use a piece of jumper wire bent in a "U" shape, but a paper clip is just about the perfect diameter to fit in the ALDL terminal sockets.

Here's how to use it:

Form this paper clip or wire into a "U" shape.

With the engine and ignition turned off, locate the ALDL connector under the dash, just to the right of the steering wheel in the driver's foot well area on some models, and on the left on others, depending on the make and year. There should be a small rectangular cover over the access hole in the lower dash trim, or at least was when the car was delivered.



Insert a tool as described above (paper clip) into the 'A' and 'B' terminals on the ALDL connector:



WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) - it will begin to flash. This is also commonly called the "Service Engine Soon" or "SES" lamp. The first code will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.

After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.

Once you have a note of all error codes, check this file for the decoding:

GM Error Codes.pdf.

You'll need Adobe Acrobat Reader to open/print the file.

If you feel guilty about not spending $30-40 on the code scanner, you're welcome to send it to me.

 

It could also be a faulty or shorted cold start injector switch (this is located on the manifold next to the coolant temp switch), which is opening that injector during hot starts, causing that aformentioned starting problem.

 

I will buy a pressure tester tonight so I can check the condition of the injectors.

I haven't checked for codes yet, but, is it possible to have a bad coolant or cold start sensor and not have it show up as an error code?

Also, what size and brand injectors should I buy if these turn out bad? As far as modifications to the car go, the car is stock right now and I want to keep it looking that way. If the heads come off I will port them myself and may install a little larger Comp cam. I live in an area with no smog testing so I may even remove the cat and install dual exhaust.

Thanks for all of the input.
Ken

 

I checked the fuel pressure tonight. I turned the ign. switch to on and the fuel pump ran for a couple seconds and I got a reading of 45 lbs that dropped to 35 lbs in 13-14 minutes.

I repeated the test and and the pressure seemed to drop at a slightly slower pace.

I repeated the test again and then clamped the pressure side of the fuel line. After 5 minutes the pressure had dropped a couple pounds.

I unclamped the pressure side, repeated the test again, and then clamped the fuel return line and again the pressure dropped a couple pounds in 5 minutes.

I repeated the test one more time without clamps just like I did the first time, and the pressure dropped almost 3 pounds in 5 minutes (slower rate than the first time, weird)

I then started the cold engine. It started a little harder than normal. I didn't need to touch the gas to get it started, but had to slightly step on the gas to keep it running and I got a check engine light. (At idle I have 37-38 lbs of pressure.)

This is the first time I've seen the light on with the engine running, but I've only put about 60 miles on the car since I bought it.

I ran a code check and got a code 15.

What do you think?
How long should the system hold pressure?
How can I test the coolant sensor?
Is the coolant sensor located in the front of the intake manifold below the throttle body?

Thanks
Ken

 

well it sounds like you have a leaking injector or injectors or possibly the regulator is leaking, it should hold a consistant pressure as far as i know, but i could be wrong (someone please correct me if i am) as far as the code 15. Low temperature indicated at engine coolant temp. sensor thats probably becasuse as you stated before the engine is running cold, simply take the water neck off of the intake manifold and see if it has a thermostat and if it does see if it is stuck open, if it is or doesnt have one at all replace it and i bet that would fix your problem..

 

I've heard this several times and made the mistake of doing it once. What exact damage is done to the ECM? The engine started fine, i just had to tap the gas pedal a bit. Although my ECM has been suspect since i've bought the car. I went to a dealership and they told me that the computer in my car could be defective depending on its part number. Is this correct?

 

If you're holding 35 PSIG after 13-14 minutes, you probably don't have a significant injector nor regulator leak. Chances are, the check valve in the fuel pump are leaking back to the tank (quite normal).

At least you know that fuel pressure is not the problem. Just for grins, disconnect the cold start control or cold start injector (whichever is easiest for you to access). The cold start control is located in the front coolant crossover of the intake. The cold start injector is located along the left side of the intake, between the #3 and #5 injectors. Neither is a real joy, but I think the injector is a little easier.

Once it's disconnected, see how the engine performs a hot restart.

 

I'll try unpluging the cold start injector tonight.

The more I look at the thermostat housing the more it looks like it has been removed in the past. The guy I bought the car from thought the dealer may have removed the thermostat.

Everything but the fluids, filters, cap and rotor are original to the best of my knowledge. (even the plugs and wires are original)

I'm going to change the plugs/wires and since I'm unsure of the thermostat I might as well replace it too. Since the sensors are original and I will need to drain the anti freeze for the thermostat, maybe I should replace the coolant temp sensor.

will a 180 deg thermostat work without causing me trouble?

Will a scanner give me anymore insite to diagnos the problem?

Thanks
Ken

 

Ok, First thing, if you want to start throwing parts at it, The fuel pressure regulator is the cheapest to start with. Depending on mileage, mine had 119,000 miles on it, my injectors leaked about that much. According to GM, you can loose up to 5lbs in a 10minutes I believe, and that is acceptable. It could be a combination of things, but if I had to pick, I would say injectors.

 

I found this place that sells these refurbished XP240Pro scanners for $144.99
It is supposed to work on GM, Ford and Chrysler.

They also sell GM only scanners for $99

Do you think this scanner would me of any use to me in pin pointing the problem with my car?

http://www.autocheckup.net/Merchant2...tegory_Code=RF

Fuel injection diagnosis and trouble shooting is new to me. All of my experience is with carbed engines but it appears that electronic fuel injection is here to stay and I want to learn all I can about it. This IROC will be a good place to start before I get much farther with my project car.

Thank you for all of the info.
Ken

 

The "$30" code scanner is not a real scanner, it just "reads" the trouble codes stored in the ECM.

If you have a laptop you already have the best scanner there is.
Go here http://moates.net/gmecm/index.html for the free software and he also has schematics for making a cable to hook from your laptop to the ALDL (diagnostic link under the driver side dash) I reccommend the 2 transistor cable, it is easy to build and costs about $8 in parts from Radio Shack.

If you don't have a laptop you can get a good one from E bay for around $50, Just get a lowly little pentium 1 laptop with an active matrix (TFT) screen and it will work great.

 

For it running rich when warm, start by changing the O2 sensor and see if that helps. After that its most likely the injectors or the cold start injector (9th injector on driver side plumbed into the base of the runners)

 

IT'S FIXED!!!!!!!

I stayed home today and installed a 180 deg. thermostat and a coolant temp sensor.

Warms right up, starts without touching the throttle and no error codes.

Thank you for all of your help!!!!

The car is supposed to still have the original plugs and wires so I'm gonna change them also.

I bought some Accel 300+ 8.8mm wires. They won't cause any problems with the computer or anything will they?

I'm going to go check out a lap top at a garage sale my friend told me about.

Again, thank for all of your help.
Ken

 

No, there should be no problem with the computer by simply changing wires. If i were you though, I'd take that Accel box back to wherever you got it and get something else. I used to buy nothing but Accel, but after going through 2 coils, an ignition module, a set of 8.8mm wires, and a distributor cap in no more than 4 months, I'll never buy Accel again.

 

I hadn't seen a response on the wires so I installed them and I just checked back and found that maybe I shouldn't have done it. Well I guess there mine now. I hope I have better luck than you have had.

Years ago I had a V8 Monza and I would hear people say how much trouble they had changing their plugs on their Monza's. Well my Monza was easy (had to remove a motor mount bolt and raise up the engine) compared to this IROC. I can honestly say I have never had a vehicle that was this hard to do a plug and wire change

On the plus side, I have never had such a big, no, huge performance increase from a plug and wire change before

The old plugs and wires were original and had 92,000 miles on them. The center electrode had eroded away creating a .050-.060 gap. The wires had corosion at most of the plug connections and the coil terminal was so coroded that it left a pile of white powder sitting on top of the coil.

The guy I bought it from had just replaced the cap and rotor before I bought it so I didn't need to replace them.

Seat of the pants dyno feels like a 20%-25% increase in power after the coolant sensor, thermostat, plugs and wires.

Thanks for the help.
Ken

 

You'll be fine with the Accel wires, there's nothing wrong with their products. I've used nothing but Accel wires, caps, rotors and coil on my IROC for the past 15 years and never had a single problem.