1993 940 w/275K. Was running fine but had an exhaust leak around one of the exhaust ports, between the head and manfifold. Replaced all 4 exhaust manifold gaskets between the head and manifold, and replaced the gasket between the manifold and down pipe. Can't find any leaks now, and the exhaust coming out of the tailpipe blows strong, so I also don't think there are any blockages in the exhaust. The problem now is that the car idles erratically after startup, has poor acceleration, and produces engine code 1-3-3 (TPS). This didn't start until after I replaced the exhaust gaskets. I've cleared the engine code multiple times, and it comes back. A couple of times early on it also produced engine code 1-3-1 (O2), but the last few times it's only been 1-3-3. I tested the Throttle Position Sensor, and it seems to be working fine. I also ran the various diagnostic tests from the ODB, and everything seemed to be working.

You didn't by any chance knock a spark plug wire loose when changing the exhaust manifold gaskets did you????

It's worth checking

I did replace the plug wires in the process, and performance improved but was still not back to normal. After replacing the EGR and cleaning the air control valve performance improved to where the car is now performing better than it was before I replaced the exhaust manifold gaskets.

I also suspect your intake gasket. There are ways to find some an intake leaks without taking it apart.

Perhaps the exhaust leak damaged the intake gasket.

You should also check your spark plugs and wires - the work may have damaged old wires, connectors, etc. An examination of the plugs may reveal where the problem exists.

I always try to keep the basics in mind - fuel, air, and spark.

Please let us know what you find.

Removed, checked, and cleaned the distributor cap, tighted all of the ground wires, and replaced the plug wires with a spare set I have. The car idled and drove better, but still isn't running as smoothly as it was before, and the 1-3-3 engine code came back again after a few minutes. The exhaust coming from the tail pipe seems much stronger (higher velocity/pressure) and hotter than normal. The exhaust manifold got almost white hot. Would this be a symptom of a faulty EGR valve? Looking around the edges of the intake manifold I don't see any cracks or breaks in the gasket. That's not the original gasket; I replaced it several years ago, but how long ago I don't recall. The exhaust manifold gaskets I replaced were the original gaskets (275K miles), but the intake manifold gasket isn't the original gasket because I do know that I replaced it before. Thanks for any insight you can share on this.

> The exhaust manifold got almost white hot

Wait, what? This was a new condition after just replacing the exhaust manifold gaskets?

It was actually glowing cherry red? Others will be more knowledgeable than me but it sounds like it might be an extreme lean mixture?

Randy

I blocked the line feeding into the intake manifold from the EGR valve. The exhaust temp seems to have returned to normal. I presume the EGR valve is either stuck open or failed open, and that contributed to the higher exhaust temp. Not sure if that makes sense. I'll do some more research on that. I plan to remove the EGR valve and check it, and I'll clean all of the intake components while doing that. It will be next week before I can get back to working on it. I'll report back what comes of this. Thanks

I removed the EGR valve w/sensor. The valve tested fine on the bench, but I had already picked up a spare at pull-a-part, so I installed the spare valve w/sensor, and I cleaned the EGR inlet and outlet lines. I also cleaned the air control valve. The car's running fine now.

Dear chrisbradberry,

Hope you're well. Thank you for the follow-up post, which is very helpful.

I do not recall a post that set forth the symptoms your car presented, so your careful explanations are truly useful.

Yours faithfully,

Spook

I had replaced the exhaust manifold gaskets after discovering a leak. Afterwards the car idled and ran rough and had poor acceleration, intermittently. It did improve some after replacing the plug wires but was still running rougher than it was before replacing the exhaust gaskets. After replacing the EGR valve w/sensor (with a spare I picked up at pull-a-part) and cleaning the air control valve it's running better than it was before I replaced the exhaust gaskets. Seems fine now.

Dear chrisbradberry,

Hope you're well. Strong exhaust flow argues against any blockage. Given your comments anent the TPS and the intake manifold gasket, I'd check the air intake hose, the corrugated hose that connects the air mass meter to the throttle body.

I'd also check the fuel pressure regulator (FPR). Has the FPR ever been replaced? Is the vacuum hose to the FPR in good shape? If too much fuel is being supplied for the amount of air entering the cylinders, the engine will run "rich".

An engine that runs "rich" often produces a carbon build-up on spark plug tips or at the tailpipe. Unburned fuel expelled into the exhaust manifold - and burned there - might account for what seems to be a "super hot" exhaust manifold.

Hope this helps.

Yours faithfully,

Spook

i would replace the intake manifold gasket