82 Crossfire running rough

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My 82 crossfire runs rough especially when cold but also at idle when hot. After start up while it is warming up it surges from around 800rpm to up to 1800rpm but settles down when up to temperature. Coolant temp sensor seems to be OK, TPS seems to be OK and vacuum seems OK. How do I check if the EGR is functioning properley? Any ideas would be much appreciated here in the UK nobody seems to know much about crossfires.

 

[terry82]

i am not sure if i understand what,,,,, seems to be okay?have you done a check or do you just think it is okay?what you have said it sounds like a vac leak .

 

[tab]

i am not sure if i understand what,,,,, seems to be okay?have you done a check or do you just think it is okay?what you have said it sounds like a vac leak .

Coolant temp sensor reading 6mv when cold and over 900mv when hot don't know what the readings should be but the difference suggests that it is working, the TPS reading is 518mv at idle and 920mv with throttle open, the PCV is clean and clear, the EGR does not appear to be moving not sure at what point the solenoid should put a vacuum on it as it moves easily enough when the diaphragm is pushed with fingertips.

 

[terry82]

have you sprayed the intake with carb cleaner to see if you have a vac leak ?check that first .you egr maybe leaking but the intake is what i would look at first .do you have a vac gauge that you can put on the egr?if not try pluging it off and see what happens.

 

[geekinavette]

Those CTS measurements don't seem right. I know I did that a loooong time ago and I don't recall the numbers...but those numbers seem awfully low.

Aside from that I would agree to hunting for vacuum leaks..particularly around the lid.


EDIT: thinking some more I do believe the CTS is a negative coefficient thermistor...so the voltage should decrease as temperature increases. I know the gauge sending unit is and I believe they operate the same. This is from memory so I could be wrong...but it may be worth pursuing.

 

[killain]

Routh idle !

My 82 crossfire runs rough especially when cold but also at idle when hot. After start up while it is warming up it surges from around 800rpm to up to 1800rpm but settles down when up to temperature. Coolant temp sensor seems to be OK, TPS seems to be OK and vacuum seems OK. How do I check if the EGR is functioning properley? Any ideas would be much appreciated here in the UK nobody seems to know much about crossfires.

I had this problem in my 84 and spent a few years chasing it down. 1. on both throttle bodies you have two "Idle control Motors" their easy to see and remove, clean and reinstall There's a procedure to setting them, look on the web and you'll find it. That said I tried all sorts of methods to find what I believe you have which is a vacuum leak. Finding a vacuum leak is easy if the air cleaner assm. in on and bolted down, However that doesn't allow you to see where it's coming from, taking the air cleaner off and now you can't hear the leak. So do this 1. Make sure you have a fresh tune-up, plugs wires and so on, timing of the engine is dead on and the fuel bodies are working fine. (Now when I say fine, the Bosch fuel injectors should be spraying the fuel and you should see it in a small cone shaped spray. If the fuel is leaking or just drippling out of the injectors that is one of your problems. They are rebuild-able and the drippling cause some cylinders to get different amounts of fuel and thus you have a rough idle.

Next is a vacuum leak. The best way to do this is with the engine idling and in park and all other things like a tune-up and so on is done. Get a propane torch, open the valve and slowly point and move it around the entire intake manifold, back by the distributor and especially around the base of the fuel injector bodies and the plate on which they are bolted, but pay special attention to vacuum hoses, "Tee's" connections and all of the other routing, Look at the line that goes down to the modulator on the 700R4 transmission is so equipped, but as you move the torch around and at any point the idle raises, you've found a leak. 20 year old plastic fittings often brake just from age and so they are prime suspects. Often the gasket one top of the intake manifold is brittle from age and a piece off sliver gets sucked in and leaves a vacuum leak.

The L-83 was a troubled motor, Throttle body injection works great, and it has been on a ton of 80's GM automobiles and trucks. But on the Corvette there was problems as the whole construction process was way behind schedule and so many things hadn't been done. I read a number of years ago that the whole intake manifold on the L-83 was a mistake and it is mounted on the block backwards, but the error wasn't found till long after the design had been approved and was being cast. That is the reason for the long throttle cables going out in front of the engine and coming back into the two throttle bodies. They had meant to be two short cables routed out of the firewall and do an 'S' turn and into the throttle bodies from the rear.

But I digress, anyway i hope I was of some help. Good luck and make sure you have patience. It's a frustrating process finding a "rougth idle".