Alright, so I finally made the purchase of the 1986 GL coupe, however it seems like it doesn't want to idle now, even though it ran perfectly two weeks ago. I have to give it throttle or it will die. It's also running rich, but it was doing this two weeks ago as well. So far I've heard that the MAF and IAT sensors might be dirty and that it might be a vacuum leak. Any other ideas?

I'll bet your running rich problem is also causing your idle problem. It'll be a good idea to get new spark plugs once you have it sorted out, they're probably pretty loaded up and that's why I won't idle.

What makes you think it is running rich?

What does the O2 sensor have to say on the subject?

 

Based on your brief description,I`d bet money it is lean.

 

Dirty IAT sensor causing problems is unheard of,

Bad MAF is almost as unlikely,

 

Turbo right?

My money is on an unmetered air leak from the rubber intake tract/associated plumbing or PCV system.

Or a vacuum leak.Put a gauge on it,

I would inspect the CTS cnnector for corrosion as well.

On the GL10's, there is an idle screw adjustment, on the back side of the round intake inlet into the top of the intake manifold.  The screw access is from the top.  Counterclockwise is a higher idle.  However, you should check the timing first.   If the advance slips to less than specified, the idle rpm also drops.  The bolts that hold the distributor in place and at the correct advance, may be loose.

I can tell it's rich by the smell. Also, it currently has an exhaust leak in the downpipe. I assume there's an O2 sensor before or after the cat, could that be causing issues as well? Oh, and another note. Once I get moving it's running perfectly fine. When I started it this morning it did something a bit differently. It idled at 1000rpm for a little bit, slowly idled higher to about 1300rpm, and then slowly idled down until it died.

Edited November 26, 201312 yr by Ziginox

Upstream exhaust leak could indeed cause rich running once the O2 sensor warms up.

Try it w/O2 disconnected.

 

The fact that it is an idle problem suggests leaness is more likely though.

 

I wish I had a nickel for every customer who incorrectly thought he could detect mixture strength w/his nose.

I'm not the only one that noticed the smell, my friend (who is an experienced mechanic) is the one that originally pointed it out to me. It's a bit late now, but tomorrow I will go out and see if I can disconnect the O2 sensor.

Edited November 26, 201312 yr by Ziginox

Same friend that thought the MAF and IAT sensors might be dirty?

No, he was only thinking MAF sensor due to the richness, and that the richness might be causing idle issues. The air filter was also slightly oily, which is another reason he thought that. I think that someone that assembled a Corvair from parts that had been sitting for years in a few days and drove it home, as well as rebuilding the engine in his truck (just to name two) should know his stuff. 

Edited November 26, 201312 yr by Ziginox

I like Naru's idea of putting a vacuum gauge on it, if for no other reason that I like to eliminate the easy/cheap stuff first. 

 

Not sure if you've done this yet, but pulling a plug or two can also give you an idea of how the mixture is doing. 

 

Not sure if you've done this, but a timing light would show if it's advancing properly. If it has a vacuum advance with a bad diafram, that could be a big vacuum leak. 

 

Just a couple thoughts...

 

John

Alright, I'll get my friend out here with those. Unfortunately I don't have many automotive tools myself.

It's unlikely that there's an exhaust leak that's messing with your o2 sensor reading, unless its the turbo/downpioe gasket. The o2 sensor is a couple inches past the turbo, most leaks are past that. X2 on pulling a plug to see what they look like. If it starts fine when cold then goes to spoob after, it's probably one of your sensors. It's running a set fuel map when cold then looking to your sensors to determine fuel ratios after the coolant temp sensor says its warmed up. So, o2 or MAF, maybe even the coolant temp sensor. Clean the MAF, and the others are super cheap on rockauto. Oil in your air filter makes me think the MAF is dirty.

I'll look into pulling the plugs myself tomorrow, and yes the down pipe is broken right where it bends towards the centre of the car. It doesn't run properly when cold, either.

Blargh, I don't have a socket to remove the plugs. I guess that will have to wait for this weekend, too...

If your exhaust is leaking before your o2 sensor, it'll cause the motor to run lean.

If your exhaust is leaking before your o2 sensor, it'll cause the motor to run lean.

 

You have it backwards my friend.

 

O2 sensor will see extra O2(that never went through the engine) from the leak  causing the computer to THINK the motor is lean and add extra fuel resulting in an intake mixture that is too RICH.

Edited November 26, 201312 yr by naru

You have it backwards my friend.

 

O2 sensor will see extra O2(that never went through the engine) from the leak  causing the computer to THINK the motor is lean and add extra fuel resulting in an intake mixture that is too RICH.

Well, as mr. sarcastic said, the O2 sensor is just a few inches past the turbo, where the exhaust leak is farther downstream.

 

EDIT: I forgot to mention that I check the distributor cap and it wasn't loose, or is the advance adjusted internally?

Edited November 26, 201312 yr by Ziginox

If either of the two vacuum pumps on the right side by the air filter, are either broken, malfunctioning or perhaps the nipple broke off, then the engine will have difficulty idling.

timing advance should occur inside the dizzy, either by counter weights, vacuum advance or the computer. on my '89, there is a green wire connector close to the fuel filter that needs to be connected for testing purposes.

 

john

injected and no one has suggested dirty injector(s) ?? If they don't spray nice, fuel don't burn nice or at all and possibly makes it rich exhaust beyond control of O2 sensor fuel trim range.

injected and no one has suggested dirty injector(s) ?? If they don't spray nice, fuel don't burn nice or at all and possibly makes it rich exhaust beyond control of O2 sensor fuel trim range.

We dumped some injector cleaner in to no avail, but still they could still be gunked up...

The distributor timing advance wears out because on the 86, the vacuum from the engine causes one distributor plate to rotate relative to a plate below it.  Ball bearings separate the plates.  The bearings get corroded and pitted, dirt gets piled up on the bearing path and/or a gough gets ground into the bearing path.  This bearing path area needs to be cleaned and inspected.  If there is impedence to the plate rotation, then the timing advance will be off.  Upon release of your gas peddle, the timing advance may get hung up at a more advanced position. Or upon application of more gas, the engine may get hung up at a less advanced position than it should be.  More advanced positions normally cause the engine to idle faster, not slower.  I have not seen a reply here where the timing was checked, because that will cause a a low idle rpm.  The idle mixture needle will also cause a low idle rpm, by turning it clockwise.  The throttle cable can be used to adjust idle higher.  If the engine is not idling smoothly no matter what rpm you are above say 800 rpm, then you have bigger problems. 

Well, turns out my friend couldn't make it out this weekend, but here's a quick video I made.

You might take your distributor cap off and check that each of the four connecting wires is firmly connected to their respective metal tab that stick straight up off of the black plastic encased distributor brains.  One may have worked it's way loose.

Well, it is indeed the MAF sensor. I tried running it with the sensor unplugged and it idled perfectly. I can't get it apart to clean the sensor though as I can't get the airbox apart because the intake boot becomes rather solid at 14 degrees (-10 for the people in smart countries.)