Okay first off I know there are a million threads about this but none of them solve my problem. The car is a 1986 camaro 5.0L TPI to start with. The problem is when the car is stone cold after sitting all night or something and I go to start it, it idles between 750 and 1500 rpm. Then I put it in any drive gear and no matter how much gas I give it, it just bogs and shudders. I've unplugged the MAF and drove it a couple blocks to check that and it made no difference. Then checked the MAP by unplugging it and starting it but all that did was make it idle at 2k. Next I went to look at EGR problems and realized I don't think I have one anymore because to my knowledge it is attatched to the passenger side manifold and I now have longtube headers. Correct me if I'm wrong on the EGR situation but I'm dying to know how to cure this.

Sorry for the long post

 

EGR is under plenum. You do not have a MAP sensor.

 

So what did I unplug right next to my throttle body? I thought that was the map? Would it be worth investing in a new EGR valve or just diealing with it since it only happens when its cold?

 

Most likely it was the IAC, otherwise if it were the TPS or CTS the ECM would turn on the SES a set a malfunction code.

4-wire connector? Then the IAC which is why the ECM lost control of the idle.

RBob.

 

Any EFI car will idle as high as 2K when first started. It takes several seconds for after start enrichment to decay and the engine to drop to normal idle. When fully cold, after start decay will take longer and warm up enrichment will continue along with a slightly raised idle for as long as two or three minutes until coolant temp reaches the normal operating range.

The shudder you are experiencing is another story. You most likely have a compression, fueling or ignition issue that is causing the drivability issue. Have you checked compression? How is your state of tune? Have you checked wires, plugs, cap and rotor? Where is your timing set? You may want to perform a KV test to be sure your coil and ICM are producing sufficient KV. Remove the distributor cap and check for runout in the dist shaft and/or heavy rust buildup on the timing core and pole piece. How is your fuel pressure? Have you ever had the injectors serviced? On a car this old you need to be thorough in your check out as most cars aren't maintained properly and there may be neglected parts that need to be serviced or replaced.

 

RBob yea must have been the IAC then. ASE Doc my timing is set at 12 or 14 degrees btdc but its been that way forever. Recently replaced spark plugs, wires are good no burns or anything. I haven't checked fuel pressure or injectors because this bog and shudder started immediately after I installed the longtubes. So I doubt its fuel related or it would've been that way before. Right?

 

I can't see headers creating a drivability issue like this. I've installed many sets and never did much more than a minor mixture adjustment to restore normal idle and throttle response. Your 86 is a MAF car so any change in airflow, which would be minor with only a header change, would be seen by the MAF sensor and compensated for. That leaves something that you changed when you installed the headers and haven't caught it yet.

I have replaced many sets of plug wires that looked great and even resistance tested okay but still caused an ignition drop out hesitation under part throttle acceleration. Don't assume yours are okay. I would use an inline spark tester placed between the plug end of the wire and the plug along with a long test wire that allows you to place the tester on the cowl so you can see it as you place a load on the engine. Watch for the spark to hit and miss. Do this on several of the plug wires.

To monitor fuel trim and general engine data, you need some kind of scan tool that will allow you to read datastream. I have always recommended a used scan tool like the Snap On MT2500, but I've been hearing alot about WIN ALDL and tunerpro. It sounds like you can get the software free off the website and just need to make a cable. This will let you see if the engine is going lean as in injector failure or unmetered air leak.

Since the problem happens when the engine is fully cold, it could also be related to the ECT sensor in the front of the intake manifold, next to the thermostat. Check the connector and be sure the terminals are clean and fit snug to the sensor pins .

 

Sounds like I may have too look at getting that software and cable so I can do one diagnostics. Also besides headers it was upgraded to true dual 3 inch exhaust. Half of the emissions controls were gone when I got the car and after everything I've done now its all completely gone. Car may very well be running way too rich but being FI the ecm is supposed to adjust that accordingly. Smells like gas horrible when it bogs. So I'm gonna look for a scan tool. If all else fails I'm months away from starting an engine swap anyway so if it can't be fixed it'll for sure go away after the swap when I change to a carb.

 

The fuel smell fits an ignition drop out. Go with the spark test like I detailed above. Also, check that ECT sensor. scan tool is a good way to find a misreading ECT sensor too as you will see ECT on datastream and can compare it to actual temp.

One other thought. Did you have to lower or raise the motor to install the headers. It's almost certain that you did. Think you might have cracked the dist cap? A cracked cap can cause more trouble when cold and damp, less on a warmed up engine.

 

Actually yes I dd have to lack up the motor to fit the headers in but I was careful I thought. Definately check that out real quick. Is there any way to test the egr valve while its in the car? I will also check the rest of the ignition system while I'm looking at the distributor cap as well. Where is the etc sensor as well?

 

The ECT sensor is at the front of the intake base, below the throttle body, just below and to the side of the thermostat. It has a black wire and a yellow wire to it.

You can test the EGR valve with a vacuum gauge by applying vacuum to it at idle and seeing if the engine stumbles with the valve open. Don't expect the valve to hold vacuum though since it's pressure modulated and will only hold vacuum when there is sufficient exhaust pressure. If it isn't stuck open, it's not your problem.

 

Okay so checked distributor and all wires along with making sure pcv has vacuum. When I can find my vacuum tester I will check egr valve. In the mean time I'm going to adjust timing to 6* btdc maybe 8 or 10 just too see if it helps and adjust idle speed after that. Should hopefully help some. I really appreciate all the good advice doc uve been a massive help so far and it means a lot.

 

Update. Adjusted the timing to about 14 or 16* btdc and adjusted the idle as well. Ran better when it got warm but ill find out if it helps when its cold in the morning. Ran rugh at first but it may help since the cars old and timing hasn't been adjusted in forever.

 

Just be sure to listen for detonation(pinging) under hard throttle. By advancing base timing, you are advancing the entire timing map. 12 degrees base may be good for your motor but if your hear any pinging, you will need to retard 2 degrees at a time until the pinging is gone.

 

I haven't heard anything yet but it definately helped the bog when it starts cold. Idle is still not as steady as I'd like it but for now I think advancing the timing worked wonders. It has stalled once at a stop light since advancing it. Is this anything that I should be concerned with?

 

I don't see where advancing the timing would cause the stalling issue. However, I do expect there's a connection between the stalling and the rough idle. Again, this is a situation where datastream may be helpful. IAC counts, MAF data, ECT data. Each of these could cause this type of issue.

 

I agree there still has to be a sensor problem messing with the idle. At least half of the problem is fixed. this weekend I will check all sensors and readjust some things and hopefully I'll be ready to go until I start the 350 build sometime. I will for sure put a vacuum gauge on the egr because you mentioned it and it may be stuck open.

 

Please post your results.

 

Here's the verdict. Idle is smoothed out and take off when cold is great. Only problem is car now idles in park at 1500rpm and 750 in drive. Sensors all operating and egr holds a little vacuum so its not open. Question before I pack up and leave it as is: should address the slightly high idle even though it runs great or leave it as is?

 

Ran the car till the wheels came off this weekend. I found that dinky hose going from the charcoal canister the the egr solenoid unplugged and put her back in. Didn't do squat anyway but at least its hooked up again. Car still idles like stated in the previous post and the idle adjustment screw is backed so far out its about to come out by itself... car has also stalled once since Friday which was kinda weird. Drove it about 45 minutes on a cruise to local event, got there and moved the car after it sat for about an hour so it was down to ab 170 degrees. That is the point where it drove for a few blocks then stalled. Not sure why or how but if nobody brings it up as a potential problem it'll stay as is.