Thanks 450,

It means that I would not replace the CHT just yet.

With the engine up to operating temp. Take the oil cap off, you should notice the engine faultering/stumbleing. Tell me if it's significant of just slightly faultering. Important: Make a mental note the level of stumbling.

Check the Manifold bolts. It can a bit challenging but if you have a swivel head socket and extension, you can get it done. (18 ft/lbs.) Make sure you get to all 12 bolts. Be cautious when tightening.

Check the hose connections behind the throttle boot and the brake boost connection (it's next to the cruise control diaphram assm. ) You have a vac. hose that goes from the cruise control to a connection there.

Check the restrictor valve. It is inside the oil neck breather hose. From the oil filler neck, you have a main hose. Pull it off and inside there will be restrictor type valve that should not be mangled or deformed. Once you look at it you'll see what I mean. Pull it out and seat it properly on the filler neck and re-attach the hose.

The boot between the manifolds under the ICV. Two clamps...Unclamp and slide the boot either left or right and clean as best you can. (that boot does not come off) It can be a pain to reclamp because the boot will expant once you unclamp it. Be patient and get it back on.

Start the car and set your idle then remove the oil cap. Compare the level of engine stumbling from before and after. What do you notice?

If I read this correctly this only happened once. If that's the case I don't think I do anything unless it starts to repeat itself. You're talking about a lot of troubleshooting here for a single occurence and depending on what you do you can start creating other issues from changes or fixes if you going down the wrong path.

The items mentioned so far are routine checks for vac. leaks. I believe by doing these type of checks it helps to eliminate the un-necessary replacement of some perfectly good working components.

You will notice that these checks can be performed in a minimal amount of time with normal tools and do not require parts.

Once the vac. issue are eliminated, you can then move on to other areas directly related to problem. Which at that time may require replacing a component etc.

If the problem happened once, it's going to happen again.

Happy Holiday's

I had a surging idle problem on my 84. I replaced the ICV, head temp sensor, and O2 sensor, but the problem remained. Then it was suggested to me that the mixture was off. I took the car in to TRE. They adjusted the mixture, and the idle has been rock solid ever since. Sometimes the simplest solutions are the best.

I agree scottb....

Those components you replaced, hang on to them, they are probably still good. By the way I bet changing out those components cost you around $400.00.

On the good side...you have new parts in there.

kqw and Scott,

Thanks for the detailed information. I've taken off oil cap off just recently in order to add a quart of oil. The engine was up to normal operating temp and there has never been much of a stumble or idle increase that I've noticed - if it has it's only been minor. I'll check it again later this morning along with all of the hoses you mentioned.

Scott, I'll probably bring the car over to Hergesheimers next week and ask them to check and adjust the mixture. That's one thing I won't fiddle with myself.

-Scott

I felt the same way. I don't mind changing out components, but when it comes to something like mixture, where I don't have the proper metering equipment, I'd rather leave it to the pros. The guys at TRE are definitely pros!

Just a not before I'm off to get ready for Santa.....

Note: When the cap is removed, you want to see a noticeable stumbling of the engine.

Well, I just warmed up the car to normal operating temp then opened the oil filler cap and noticed a slight roughening and decrease of maybe 30 to 50 RPM - nothing much but it was noticeable.

The guys at Hergsheimers seem to think the culprit is most likely the mixture so I'll probably bring it in to them in a couple of weeks - after the new year.

-Scott

Update (JeremyD pointed out to me that I never resolved this thread - sorry guys).

Anyway, as stated, I finally gave up. I took it to my mechanic (Hergesheimer), they hooked it up to a gas analyzer and found that the idle mixture and idle speed, which are apparently co-dependent, were way off. They adjusted it perfectly, tightened up a few straps which secure the 90 degree rubber elbow to the AFM and throttle body and...

It ran perfect! It has run absolutely flawlessly since that day. It turned out to simply be the base idle mixture and idle speed settings that were significantly off their marks which was causing the whole mess. Interestingly, the idle speed shown on my tach had seemed to be within the normal range so it never entered mind that it and the mixture were way off. My mechanics said that many of these cars have the same mixture/idle speed problem and a good adjustment with a gas analyzer usually cures the problem.

I hope this helps anybody who comes up on this issue in the future. Check (with a Gas Analyzer) your base idle mixture and idle speed settings. Many times these settings are the real culprits here.

Thank you.

87 Blk Coupe