88txiroc

Ok, I was driving my IROC (350) about 2 weeks ago. It was running great. Went into a store for about 5 minutes and came back out to go home. The car started just fine, but felt as if it was running on 4 cylinders. I hope that makes sense.

It idles just fine, but when I accelerate, it sort of "misses". I used my Auto Xray and there were no trouble codes. All of the numbers look right where they should be.

I checked the plugs and wires to make sure they were tight, and they were. No exhaust leaks that I can find.

What should I check next? I have a shop manual, but am kinda' lost as where to start. I looked through quite a few pages on TGO, but can not find anything that resembles my problem. I am sure someone has run into this before, please help. I can provide any other info required.

Thanks, Thomas

Air_Adam

Spark plugs good? Are they all plugged in tight?

WaynesIroc

Probably the MAF sensor. try unplugging it and driving with it unplugged. If it straightens up then the MAF is shot. I just had this happen to me recently and that was what it was.

onebinky

iTrader: (1)

Start with the basics, make sure the engine is getting it's air, fuel, and spark.

Pull the wires off, and do an impedance check on them. Pull the cap and make sure the contacts aren't all corroded and nasty looking. Pull the plugs and see what they tell you. Rich, lean, burning oil, not firing, etc...

Throw a fuel pressure gauge on the rail and see that you are acheiving and maintaining pressure both at idle and under load.

When was the last time you changed the fuel filter? The gm filters are notorious for clogging, even after a low amount of mileage. That can seriously reduce the amount of fuel the engine can get. While this may provide better fuel mileage, if it gets bad enough it'll kill performance and drivability. If the pressure does show as low, keep in mind you have an in tank filter (sock) as well.

Air filters clean?

Just for kicks, take a look at your cat after the car is running for a little while. Is it glowing red? If that's the case, it's clogged and needs replacement or removal.

Any enemies? Check the tail pipe for a potatoes stuffed in there

Also, the earlier GM EFI cars like these really only have the trouble codes for things that effect emissions, so alot of drivability things won't show up. Alot of the times if there is something wrong with an emissions thing, the trouble code still won't show up

Start with this stuff and see where it leaves you.

Good luck

onebinky

iTrader: (1)

EDIT: Also make sure that the wires aren't cross firing.

Start the car up at night and spray the wires with water. If they are cross firing, you'll get a pretty light show.

acescarrsRS

Like mentioned earlier, you can check for cross firing. Easiest way is at night & just check for those arcing sparks. That can cause your car to run like s***! Also, try pulling all your spark plugs. Number 8 cylinder on small block chevys are always famous for burning & your spark plug could be fouled on that cylinder. Both of these symtoms will cause the problem you are describing & I know from personal experience. Just food for thought.

88txiroc

Hey guys,

Thanks for the replies. I have been checking everything for the last few hours and nothing seemed to be helping. I checked all the plugs and wires, and changed the cap and rotor with a spare set that I had. No help at all. I disconnected the MAF and it had the same problem.

Then I had a brain storm: I decided to disable my MSD 6AL box. Guess what? Runs perfectly! I think I will try to rewire it tomorrow and see if it helps. If not, will MSD fix the box? Dont want to spend another 200 for a new one.

Thanks again,

Thomas

onebinky

iTrader: (1)

Dang, I should have thought of that. My brother had the identical problem on his 91 TA with the 6AL box. If it's still under warranty, they'll fix it for free. If not, they'll charge you but it will be put back to brand new specs.

Glad to hear you found the problem!