I just bought an 84' Vette that runs bad. It is very hard to start, idle rpms surge, appears to have a missfire sometimes. But no codes, good fuel spray pattern on the inj. and they don't drip, TPS sensor measures ok any ideas?
I would take a harder look at the EGR. My 82 EGR passed all the basic checks but still had a weak spring. I tried everything before someone caught it. Car runs 100% better than it ever did. Worth a try before digging into all the other possibilities. Also check the THERMAC for proper damper operation. I'm not familiar with the 84 Cross-fire so you may not have the THERMAC.
Best of luck.:cool
This one doesn't backfire through the TBI but does appear to have some valvetrain noise. Going through valves right now. Also a friend has a scanner and he ran it through and said the knock sensor and others were working, Unless they could be giving a dummy reading?
Thermac air cleaner uses the damper on the air cleaner inlet to control air temperature to the carb. A temp. sensor locate in the air cleaner assembly closes the damper until air temp at manifold reaches about 100 degrees then slowly opens.
Check your IACs there are two on a Crossfire if one sticks the car will have a rough idle because one side is running leaner than the other, just remove the air cleaner assembly, use a flash light and look in the throttle bodies in the trangle hole you will see the pintels of the IAC, now just goos the throttle with the car running and warmed up you should see the IACs retract then extend, both of them and they both should move about a 1/4" at least if not I would recomend you replace both. Also a Crossfire is real bad at fouling out plugs if it gets started and shut down with out having a chance to clear itself out, very rich start up! You may need to also check your plugs and keep them clean, but I bet one of your IACs is stuck.
Also there are no EGR codes on an81 to 84 vette that started in 85 with the use of a temp sensor on the EGR valve itself then moved to the cross over tube in 86 to 89, and after that they use a combination of sensors to determin if it is working.
Pistonhead, Have you manually, with a scanner,
checked the cold value of the ECT sensor? I have
replaced many of these ENGINE COOLANT TEMPERATURE
sensors for having a faulty cold start value. Also
the 1984 and 1985 models were known to have too
cold of a coil (via factory bulletin #85-C-22A-6D) Good luck, Hopper..
Did I talk about the coolant sensor I just never remember which post I post what, there was a problem with the 82 and 84 coolant sensors they used a barrel connector that was real bad at loosing contact that would just dump fuel when trying to start it you could also get some surging if it was changing on you the fix was a kit that came with the later style sensor that was a two pin sensor and a pig tail, if your car has the round barrel sensor on it just replace it and de done with it. Also the campaign to replace the coil and module and spark plug gap had to do with trying to put tomuch voltage through the wires and over heating the coil and taking it out so they shortened the saturation time of the coil with the new distributor module and then replaced the coil but this also required and reduction of spark plug gap from 0.045 to 0.035, so you might also want to check that you have the correct spark plug gap, that could also give you some problems. Boy there is so much you have to remember on these cars.