Jon92TA

1992 305 TPI Auto

The other day (6-6-06) while running errands the car was running smooth and fine. I fired up again after a short stop and the engine feels like it has a dead cylinder. It was due for spark plugs so I put new ones in, checked and cleaned up the cap & rotor, and checked the plug wires with an ohmmeter, and it still has a miss. Hoping maybe I crossed a couple plug wires I double checked them again but were all good.
The plugs that came out looked pretty black and all looked about the same.

I pulled wires one by one from the dist cap looking for a dead cylinder, no luck.
I pulled the vacuum hose from the FPR, no gas, didn’t change the rough idle rpm, it will rev up though still rough.
Checked the new #1 spark plug and it is black already.
Once it warms up a bit there is a sulfur smell from somewhere. Bad cat maybe? It’s OE w/175k
Not sure how to check the egr.
I don’t suspect the O2 sensor (15k on it) because the miss is there even on cold start.
No ‘check engine’ light.

Any ideas?

Anything else I can check?

Vader

It could be a clogging cat or otherwise restricted exhaust. It could be a stuck injector(s). It could be excessive fuel pressure. It could be a restricted intake. Might even be a MAP reading a little high (low vacuum) or a serious loss of spark energy.

Try clearing the ECM so it runs with the very basic backup parameters. If it still seems very rich, check the exhaust restriction possibility.

Jon92TA

I did put a finger on each injector and could feel each tapping, #6 was kind of weak but there.

When I was pulling each wire from the cap they all seemed to have good spark. 5 & 7 made less difference than others.

I don't think the intake is restricted, it has a fairly new K&N. When I took the plastic ext tube off the TB it seemed like intake suction sound was louder than normal, if that makes any sense.

How do I check a MAP sensor?

I'll disconnect the battery this afternoon to clear the ECM and give that a try.

I have a dual-cat that I plan on installing on the 23rd at a friends house but he lives 20 miles away. Will anything be damaged by running too rich or with a clogged cat or will I just burn more gas?

Jon92TA

I disconnected the battery for an hour then fired up again, still chugging and running rich.

BretD 88GTA

Jon,
How old is the Ignition Module? Might be due.

Jon92TA

I'm sure it's original.

I didn't suspect it because there seemed to be good spark energy when I pulled wires from the cap, and it will still rev up though still rough & rich.

What are the usual symptoms of a bad ignition module?

kurfbird

iTrader: (24)

I had the same sysptoms. Ended up being the timing chain.

BretD 88GTA

I've had them do different things. One time the car started missing occassionally, then just up and quit one day. It would re-fire but only run for about 30 seconds then quit again. Forget trying to give it gas.

Another time, the car startin running rough and ran like it was down a cylinder or two. I pulled over to see the exhaust manifolds glowing cherry red. The car would run, just very poorly.

If you do decide to change the IM, go with an AC Delco part. Stay away from Accel. Their IM's are junk. I've had them fail 2 or 3 times on me.

Jon92TA

Checked ohms on the injectord tonight #1-7=17 #8=2

So 1 bad injector, also while it was running and exhaust smelling like sulfur I looked at the cat and it had started to glow.