I bought an 89 IROC with the 5.7 for my son and I to restore. In general it's in great shape and in our efforts to get it back to original we are having difficulties getting it to idle smoothly. I had an SES light but I replaced the O2 sensor and it has stayed off. We changed plugs, wires, cap, filters, all of the injectors. The engine runs good at speed, doesn't hesitate or bog off idle. However when it idles down it seems like it loses a cylinder. It is completly stock with 63000 miles puffs a little grayish blue smoke when you start it.
I had increased the timing 4 degrees on the stock engine and I am wondering if the computer is not working well with this. Also when I put the injectors in I used a silicone sealant along with the gaskets. Now I've learned that might not had been the best thing to do. Oxygen sensors don't like sealants, is this true? New to this forum, first post hope you can help us out.
Thanks

 

Since you didn't mention them yet try using this tech article to check/reset the TPS (if 89 had an adjustable one, don't recall now) and set the minimum air for the IAC if you haven't already: https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

BTW it would seem the first step in resetting the IAC got left out if I'm not mistaken, need to disconnect it's plug before setting the minimum air.

Perhaps those will make some difference for you...

 

Thank you I will begin there. The SES light came back on again too. I guess I will need some sort of code reader too. What do you think about the gasket sealant I used on the runners and plenum?

 

Welcome G.W.W.-

IMHO, I would return base timing to the recommended 6 deg. static timing/ecm disc.

 

In the tech section there is a section that shows you how to jumper your ALDL connector to read the SES codes. You don't need a code reader.

The silicone you used on the runners could ruin O2 sensors if it's not "O2 sensor safe".

Have you done a basic compression test? Low comression would be most noticable at low RPM (idle) as would a vacuum leak.

I'd:
1. Draw the code
2. Check the silicon to see if it's O2 safe (though that won't cause the idle issue you're talking about, IMO.
3. Do a cylinder balance test
4. Check the runner for the cylinder that's not working at idle for a vacuum leak, then comression test it if no leak found.
5. Come back on here and post the results of all of the above.

 

an 89 iroc timing base is 0º stock. going to +4º may be excessive depending on your case, but that's not going to cause your missfire. i'm not sure what reason you had for putting crap on your gaskets. that's kind of the point of a gasket, never put sealer on them unless it's a required thing from the factory. not only can you cause problems with silicone that can be sniffed out by the 02's, but you can cause a leak. if the factory can put the whole engine together using silicone in only a couple of area's i don't think you're going to out engineer them. replace the gaskets you put the crap on to start with. if a runner has developed a vacuum leak you can get a bad miss at idle. if the 02 is picking up some incorrect info it will bring the LT fuel trims to a point that can cause a miss also.

 

How to pull a SES code © TGO moderator Vader:


First, you'll need to acquire a GM OBD I ECM Diagnostic Trouble Code Retrieval Tool (commonly known as a paper clip to TGO members).

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 Firebirds, and on the left on Camaros. There should be a small rectangular cover over the access hole in the lower dash trim.



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.

 

Wow a lot of info came my way. I very much appreciate the time everyone of you took to respond. I'll try my best to respond to all of you here. I reset the timing to 6 and then I checked the IAC and it seems to be working well as it should. However the TPS doesn't seem to want to go past 3.85V at WOT. I can set it at idle to .56V and it climbs smoothly until just before WOT. Where it just stops. Once or twice it spiked to 4.7-4.9 V but went back to 3.8 on my digital meter. Seems to me I need to replace the TPS.
The gasket sealant does not appear to be O2 sensor safe and I will remove it and replace the gaskets. Sorry a bit of a vapor lock on my part, I will remove the "crap". First though I am going to check for vacuum leaks just to see what I created and what might have already been there.
I may have a leak at the brake booster connection. I noticed the clamp is missing. I also noticed a bit of engine oil puddling up along the outside edges of the intake manifold. Sort of near the middle bolts. I might be pulling a leak around these bolts. When I take the plenum and runners off I'll pull these bolts out and use some sort of thread sealer on them.
The car has always idled a bit rough since we bought it but it's performance otherwise is still impressive. I have made improvements to it with everything I've done so far but this last glitch has me stumped because of my limited knowledge of emission and computer control cars.
I think I will look at the compression a bit later, though I'm not ruling it out. I'm thinking that the problem is more emission or vacuum related. I should state that the severity of the rough idle changes with temperature of the engine and sometimes it just seems to change. Other than the idle the car runs hard and will still boil the Goodyear F1s. Hell of a thing for a 50 year old to be doing, smoking tires on the freeway on ramps.

I will continue to check back and keep you posted thanks. Perhaps I will post a picture of it next time.
GW

 

If the silicone already ruined the O2 (which it is VERY likely) you need a new one.... And when it comes to replacing sensors, I am a firm believer in using GM parts..... makes a huge difference

 

The Camaro is still tore down. Upon inspecting my loose middle intake bolts for the cause of the puddling oil I found that some of the gasket is blown out too. When I used starting fluid I didn't detect a leak but non then less I am going to lift the intake and install new gaskets.
xlr8torz28

I am going to take your advice and use a GM O2 sensor. I have heard that before. I will post new on the situation once I have some news since this is getting slightly out of date. With work and the rest it may be few days before I get the car started again. GW

 

I haven't had a problem with a bosch o2 sensor yet. I wouldn't go replacing it if you haven't run it very much unless you're sure it's bad.

One thing that you may run into later regarding oil puddling on the intake manifold is that when the engine is warm, oil vapor can work its way up the threads and puddle there.

As far as the brake booster there are no clamps IIRC on these vacuum lines because they are barbed and they tend not to fall off.

One thing I didn't notice you mentioning was the pcv valve. It's a good cheap thing that you can look to replace, and check the hose for cracking as well.

Cleaning the throttle body is also something that sometimes produces a noticably smoother idle in these cars.

No sealant necessary on the fuel injectors, but oiling up the o-rings can make it much easier to slip them into the manifold.

 

I finshed last weekend replacing the intake gaskets, a new O2 sensor, a few other sensors too while I was there including the EGR. Inspected the distributer and found it to be in poor condition internally. I replaced it with a rebuilt from NAPA.
The car fired instantly. I went through all of the settings and timing again and this all made a huge difference. Idle is quite good except when it's cold and then it has a very slight miss. Power is better and very smooth. I took it for its emission test and it passed easily. it didn't before.

I'm not really sure if I could make much more improvement on the idle. It really is pretty good.
Though I will check a few more things.

Thanks to all of you for the pointers and links to various how to's.

 

Great to hear that you car is running better. I am not much of a mechanic but went through similar issues that you just worked on. Did all of the things that you did and then some. I had to replace the MAF on my car twice to get it to smooth out. I am not sure when these cars switched to speed density - but if you have a MAF car check it out. Also, because of the low mileage my car dramatically changed in idle and performance when I replaced the fuel pump. Sitting with little use somehow affected it. Your car seems to have low mileage as well. I hope this helps - It drove me crazy trying to figure this out.

 

Thanks for checking back. Yes the car is running much better. Smokes less at start up and it has picked up in performance too. There still is a bit of a miss now and then. Like you I have been all over it. It's going in for an air condition service. It cycles like crazy when first started and for the next five minutes or so.
After that's done I am going to look at the fuel filter and pump. I checked fuel pressure and it's good. All in all I love how the car drives and handles. I put Goodyear F1s on it and boy do they stick.
I use to be an auto painter/bodyman for 15 years and I've cleaned up my old guns and getting ready to shine her up. I'm an engineer now and I drive it to work daily. It drew quite a crowd of engineers looking at it the first week. I've even had neighbors I've never met come over to look at it. That says something about a third gens class when a 16 year old car can do that. I've got new decals, weather strips, and mouldings. Cool...
I'm going to keep it as close to stock as possible. They are too hard to find like that and it drives too nice to muck with it much.
Told my wife I want to get another one. She likes to drive it too!
A yellow convertible.
Jerry

 

You are going after this like I have. By what you said here you are probably near my age. I wanted to buy these when they came out new but lacked the ability. Now that I am older and have ability - I jumped deep into my project. I understand the desire to build it up and do it right as aggressivley as you are. Enjoy the project - they do not build them like this anymore. I have a 93 Z28 - fourth gen car. No comparison in fun factor. The fourth gen is a gorcery getter - the third gen is a sports car.
Have fun! It is going to take a while to get all of the bugs out but it is worth it.

Tom