I have an '87 NA, all stock except for a recently gutted catalytic converter. The car starts, although sounding extremely rough, and continues to warm up as usual. Once the rpm's drop, however, the car dies unless you give it gas. If it does die, the car starts right up again and repeats the process. The entire time it sounds very bad, and loud. The only things I can possibly think might be wrong with it are a leak in a hose somewhere, or maybe something is stuck open in the air intake pathway. Is there a way to test for any of this? Is there something else I may be missing? I really need to get the car running soon and appreciate your help.

 

Let me bump that for you

my 2 cents:

- big vacuum leak

- bad TPS

- bad BAC valve

- bad timing

Also, double check that all vacuum hoses are properly routed.

hugues -

 

yep sounds like a vac leak to me...

 

So if it is a vac leak, is there a relatively quick and easy way to test for this (ie, where is the leak)? Like I said, I need to get the car going soon, so the quicker the better. I did a visual inspection of the engine, as it almost sounded as if something were caught in the fan (but nothing is), and all the hoses appeared to be connected properly. So now I just have to find the leak . . .

 

get a can of carb/intake cleaner and spray that around the vac lines...if there's a leak the engine will rev up for a sec or so...that will be where your vac leak is...if you can't find the vac leak with a good visual.

 

Has an apex seal ever broke off in the engine?? My car ia acting like this and i was starting to wounder if this could be the reason....

 

yeah,
you should do a compression test first. No need to look at anything else if engine needs a rebuilt.

Hugues -

 

I tend to think the problem is more of a vac. leak than an engine problem. I just gutted the cats last week, and the engine was checked then. The seals, compression, and timing were fine. I know they can go any time, but I tend to think that's probably not the problem. I'll have to try the carb cleaner trick (when I have a helper, as someone has to keep a foot on the gas or the car cuts off).

 

ok, acrouse, if you think it's vacuum leak, look for the non-obvious ones, like at the ACV and EGR valve.

The ACV valve has 3 (I think) diaphragm activated valves. If the diaphragm is gone, you'll have a vacuum leak. I am sure if you search you'll find more info if you desire so. Hey, you might want to download a fsm manual (www.fc3s.org how-to->manuals, get chapter about fuel and emissions system), there is everything you want and don't want to know.

Same idea for EGR valve. Has 1 diaphragm. Note that a stuck open EGR valve can give you a shitty idle.

In your case,
I would think you have a massive one that should be easy to find if that is actually the problem.

Why not just tighten the dashpot or the 8mm locknut on top of intake chamber to keep the throttle plates pretty open. Then no need for an helper.

Hugues -