Hey guys,

I have an 89 IROC 5.7 (350) that has a problem.

Car starts fine, idle seems to be ok but... Just off idle when you first start off there is a hesitation and the engine vibrates / shakes a bit, you press thought it and it seems fine until it changes into 4th gear at low RPM maybe about 40 MPH the engine shakes the car like hell. Push the throttle and you can get though it or drop it back into 3rd manually and it runs file. Floor it and it seems to run fine, lots of power. No codes at all.

I had to take the car in for emissions testing last week. Here in Illinois they put it on a Dyno and actually drive it under sumulated driving conditions while they sniff the tail pipes. Any way it comes back telling me that there is RAW gas in the exahust, it is running way too rich and fails that portion of the test.

I had to take it to a garage to get it looked at, this helps when you are going back for a fail emissions test. The garage replaced the fuel pressure regulator, I had an adjustable one on there and the tip where the vacume line connects was broken. Then put a standard FPR on it and told me that it was not showing a rich reading anymore. I think that they just put it on the computer while it is at idle to check it. I picked the car up and the problem seem to be even worse. It has been taken back to the garage.

The garage has replaced the FPR and Spark plugs and checked the timing, they told me that the plugs were shot from the rich condition. Yesterday (Sunday) I went over to the garage and in thier parking lot I replaced the sparkplug wires, Cap / Rotor. I disconnected the ACCEL 300+ ignition and coil and hooked up the original ignition and coil. Although it seems that the car it running a little better, the problem is still there.

I believe that the RICH condition comes on just off idle and at low RPM in 4th gear. This is why the emissions test shows it and the garage does not. The mechanic has now driven the car and has witnessed the problem and tells me that "at some point during a brake tourque it seems to loose all cylinders" He does not yet know what the problem is. I think it is flooding out it is killing the engine and that the problem is fuel realted and not ignition related.

I am thinking TPS or IAC or something like that. All the garage can do is toss parts (and my money) at it until something works. Are there any mechanics out there that actually troubleshoot and repair things or are they all just parts swappers? I am stuck with this as the emmssions guys frown on you doing this stuff yourself. The Garage called today and told me that they are going to try a new distributor to see of that works. Any advise or help would be appreciated.


Rick.

 

I have been through the IL emmisions system, it's tough but the good thing is that they don't test for NOX. Which means that the way to pass the test it to run it lean and hot so that it burns off all the HC's(the raw gas). Normally this would send NOX through the roof but they don't test it.
40 MPH seems too slow to be in 4th, this could be caused by a missadjusted TV cable to your trans, the is an tech article on this site on how to adjust it.
When I went through emissions and failed the first time they gave me a list of shops and there success % of passing the test.
Since you have been running rich your cat may be damaged from the excess fuel, you will need a functioning cat to pass the test.