throttle/idle problems
 

i dirve an 86 gxl with a rebuilt, streetported s4 motor and a stock s5 turbo. all emmisions have been removed. it has a new fuel filter, 550cc primaries and 680cc secondariesadjustable fpr w jegs fuel pressure guage. secondary tb butterflies, fast idle cam have been removed. (i boutght the car all done up like this to learn about the engine, and already have something quick. bad idea).

the problem: i was driving on the interstate and my egi fuse under the hood kept blowing. ended up being a short in my fan wiring (clutch fan replaced with an efan). on the way back, the car spun a wheel bearing, the front driverside outer bearing to be exact. i have fixed the bearing, however, the engine will not hold an idle, and the throttle is very choppy when i accelerate. also it seems like its not getting as much boost, more than likely due to the lack of throttle. it also smells like its running VERY rich, i kno a rotary should run a little rich, but not this much. and i know, i need a wideband, but im trying to solve this first. my pockets are exactly as deep as the atlantic you know?

attempt at the solution: my friends with rotaries suggested i check the tps. and so i did. it should read about 1 ohm at rest, and about 6 at full throttle. it was about 2.63 at rest, so i adjusted the screw. it wasnt at 1 ohm untill the screw was almost all the way out. at full throttle it was 5.66. it feels a little better, but still sorta choppy and will not hold the idle. ive had a few people turn the screw at the throttle but no results. i checked for shorts somewhere but no luck there either.

If theres a certain sport i need to look or if someone knows of this problem please help me out. thank you.

This could be simple but is likely not so. How well does the car start?

When you say choppy throttle, do you mean that the engine misfires when you move the throttle? Does the engine rev quickly?

My initial thought is that you have a vacuum leak, but I am not seeing how that would relate to the blown EGI fuse. I am hoping that you weren't boosting when the EGI fuse went out.

You should check compression at some point if the car is hard to start. If it starts easily, compression is not likely to be the issue.

sometimes a rich smell is an indication of lean misfiring. You might also check fuel pressure, but I don't think that is the issue.

by choppy i mean it sort of misfires. sorry i wasnt as specific as i should have been.

The EGI fuse is fine now. however, i finally got the engine to hold an idle yesterday, but it only idles 2k and up. Any lower than that and it dies out quickly. the cars temp is also about half instead of its normal quarter now. my fuel pressure is at 40 in idle, cant say what it is under a lod because i cant really put someone in my hood lol. i have a feeling there could be a vaccum leak too, due to the fact that as the car runs, it just doesnt sounds the same. but i have no idea where to start looking.

Check for a vacuum leak. If it won't idle under 2,000 that would be my assumption.

Would that also cause it to go through gas like a camel drinking water? Because that's what it's doing. I'm talking like I put 6 gallons in and only drove 51 miles and it was on E.

Check compression too, this is really sounding like one-rotor operation to me.

Better yet, unplug the spark wires to the rear rotor and see if it still behaves the same. If it won;t run at all, try plugging the rear rotor in and unplugging the front one.

How quickly will the engine rev?

It ended up being a vacuum leak. There's a 3/8 hose fitting next to the throttle. When I plugged it the car ran fine. Re adjusted my idle and drove off. Stopped by the park to eat, shut it off. Started it again and drove off.Went to the store. When I came out it wouldn't start. Unplugged the vac, no start. Sat for 10 Mins, started. Went him. Now it won't start. I'm wondering if there was a hose going to something. But o font see one..

I'm glad it was just a vacuum leak, it has been too long since I have seen a stock turbo to know which hose you are speaking of, but if it ran fine up until the point where it didn't- something had to be plugged in there

Can you shoot us a picture? Given the larger size (I'm assuming inside diameter), it sounds like that fitting should be connected to larger (4 mm inside diameter) hose that goes to a plastic "spider" (a little plastic 1 into 4 manifold) that feeds air bleed air through vacuum hoses to each of your oil metering pump injectors. OR if you're underestimating the size, there is a larger nipple that connects to a vacuum hose (8~10 mm ID, IIRC) that goes to the brake booster.

below that red hose you can see it. sorry i couldnt get a better picture of it. also i know a picture is worth 1000 words, but my only personal computer is on my phone and im not sure how to upload pics from it. (picture is rotated 90 degrees counter clockwise. im not very computer savvy). that "fitting" or "opening" or whatever you want to call it was pushing a lot of air when it ran. like i said, i see no hose that looks like it came off or anything.

You're talking about the nipple where my arrow is pointing to (see attached pic), correct? That looks like the vacuum nipple that is supposed to connect to the brake booster. Without that hose installed between that nipple and the power brake booster, you have no power assist on the brakes! Note also that this hose should have a plastic one-way check valve installed inside of it.

Yes that's the nipple, but what could that have to do with the car starting?

By the way from my experience with a ported and turbo motor wideband and stand alone ecu are sooo helpful beyond words. I went from like 10mpg to close to 21mpg. Also able to finely tune out the lil hic-ups my baby had. Others like calling him a chic and cutting off in the middle of the interstate I just blame it on him being pissy. ;)

The stock ECU relies on the fact that by design ALL the air that engine burns is supposed to go thru the air flow meter (AFM), which the ECU uses to set the correct air/fuel ratios. More air flow means more fuel is injected. Having a vacuum leak that large results in lots of unmeasured air bypassing the AFM, resulting in a very lean AFR. This could make it difficult to start, but it might not be your only starting problem.

Well, everything on the brake booster is hooked up and checks out. so I decided to tear stuff down till I found what the nipple goes to. It goes into the upper intake manifold. I believe it's a vacuum line for the air control valve which has been all blocked off. So I plugged it back up. Im assuming that something else must have gone bad from the car
Running with a vacuum leak that large. Now I just need to find out what exactly it was. A task at which I am once more stumped lol.