Wolfpack

Ok heres the deal. Guy I know from work just got an 86 Iroc with the 305 TPI auto. Car was sitting for awhile and wouldnt run correctly so they gave it a full tune up, had to change the Injectors(bad gas) changed the Fuel Pump, replaced the MAF, Replaced the ECM(from my 86 Iroc) checked the TPS, IAC and Timing. Car isnt throwing anymore codes yet still has a Noticable Miss at all RPM's. The Mechanic is about to tear his hair out and I dont have a clue whatelse could cause something like that.

Suggestions Plz!!

Vader

In all that diagnosis, has anyone tesated cylinder leakage percentage or compression? Poor compressoin on a cylinder or two can create that problem.

Wolfpack

I asked the Mechanic about that actually and he said he hadnt done a leak/compression test yet since all the FI problems. He did say that the Plugs when he removed them looked normal though so he didnt have any reason to suspect that.

One thing we have noticed is that once the engine warms up it runs better though it still miss's.

vernw

iTrader: (2)

Might also check the ignition module in the dizzy, but definitely the compression and leak-down tests. Also check for plug wires arcing to headers, cracked plug, or loose plug wire. And of course, the old stand-by, a vacuum leak.

Have you done any data logging? Is the CTS working okay?

Wolfpack

I'll pass on the info so far. Dont think he's checked the Ignition Module yet, Plug wires and plugs have been changed.

It does have a small exhaust leak though i wouldnt think it would cause a miss like what I heard

No Data Logging since he isnt setup for that. He has said that he's hooked the car up to a scanner and everything appears ok now that the new ECM is on. I dont know what CTS Stands for so couldnt tell ya on that

Thanks for the info so far.....will pass all this along

vernw

iTrader: (2)

Coolant temperature sensor

If the exhaust leak is anywhere on the side near the O2 sensor that can cause you lots of fuel mixture problems. Need to make sure it's in closed loop as well. If it has headers you usually need to convert to a heated O2 sensor to stay in closed loop at idle....

Wolfpack

Excellent info...Gonna relay all this info the owner today...hopefully we get it running good soon as the car is really in great shape body wise. Thanks

vernw

iTrader: (2)

So how did it end up?