Engine Problems
 

Hey guys, I’ve been having engine problems with my GSL-SE. When I start it up after it’s been warmed up it idles at like 100 rpm. When I rev it over 3500 it bucks like crazy. It seems almost as though there is a fuel delivery problem but I checked the fuel filter and it’s clean. I also checked the fuel pump and its working. When I look at the exhaust it appears to be running rich. I then swapped the O2 censor but there was no change. I also cleaned the plugs and checked the wires but again there was no change.

And so I’m pretty much out of ideas right now. Any thoughts?

Thanks

The bucking at 3500 rpm sounds like an auxiliary port problem. Are they opening? Peruse the faq thread at the top of the forum. There is a trouble shooting section for the SE's. Download the 85 FSM and and go through the engine, emission and fuel sections for trouble shooting.

Have you tested your ignitors? Or swapped them? I had similar symptoms with a failing leading ignitor.

Well I dont know if this is right but I wanted to ask....what about the counter weights? If they are wrong could they cause this to happen? At least the bucking part?

No, the wrong counter weight will cause a vibration, which may be small enough not to notice but enough to prematurely wear bearings.

Oh gotcha. It was a thought so I figured if it wasn't the problem it would still get answered. Thanks.

Alright, first I’d like to thank you guys for your suggestions, I’ve checked the auxiliary ports and they appear to be opening and the injectors seem to be fine. Anyway, for the last 2 nights I’ve basically been reading through the Haynes manual and swapping out anything that could possibly be the problem. Unfortunately I have not had much luck with this.

The current symptoms are:

Low and lumpy idle – 200 rpm
Engine running rich
Black smoke coming out of the exhaust
Engine surging when over 3500 rpm

Here’s a summary of what I have done thus far:

Disconnected BAC air hose to allow more air into the engine – rpm picks up to 900
Removed induction manifold – pulled both injectors
Reverse blew compressed air through the injectors – found one to be passing air – swapped it out with another injector that was seating. After doing so the engine was still lumpy at idle but had improved somewhat. I then test drove it and the idle evened out at about 900 rpm, the surging also seemed to go away. However, after the engine had cooled down the problem returned.

I then changed the following:

ECU, atmospheric pressure sensor, leading and trailing coils, BAC valve, thermister on induction manifold - no change – pulled the spark wire on L1 and the engine smoothed out – changed the plug and the problem came back – swapped leading and trailing coil wires and the idle became somewhat smoother but it was still about 200 rpm, still rich and it still surged at 3500 rpm. I tried driving it around the block again as I had before however this time it did not improve.

I apologize for the length of this post however I am now back to where I was 2 nights ago when I was out of ideas.

When was the last time the injectors were sent out for service? Fuel filter new? The black smoke can be an indication of sticking injectors, the O2 sensor will have no affect on idle or accelleration, it only comes on line during steady state cruise.

Clean and test the bac, check the tps setting, look for vacuum leaks. Does the engine rev to 3k rpm at the beginning of a cold start, then drop to 2k? If not, check the cold start assist and linkage. Take the intake off at the throttle body and check that the secondary butterflys are opening.

That should keep you busy for a while.

Well, turns out the problem was a stuck fuel pressure regulator. Now it idles almost perfectly at about 850 rpm and accelerates as smoothly as it ever did.

Anyway, thanks for the help guys.

Fine job on trouble shooting. How did you figure out it was the fpr?