I seem to have a strange problem. I was driving the other day and noticed that my car wouldn't idle, it would stall. If I took my foot off the gas I heard a relay click and the car would stumble and stall, but any throttle input, even the slightest, would click the relay on and it would continue to run. The next day the car would start and run at higher rpm (like above 2500-3000), but I can't seem to get it to run on the lower end. I can't hear the relay now because of the loudness of the exhaust I have on it, which is rather quiet below 2000 rpm. I've changed fuel pumps, fixed all fuel leaks, and still no fix. Any input would be wonderful! Thanks!

 

BTW, this is my only car and I have to work on Thursday, so I hope someone can help soon!

 

Bad afm perhaps?

 

It's been working fine until recently... Is there a way to check it somehow? And how sensitive are they? Will a bit of banging around break them? I just put on a cold air intake...

 

Well there is a switch in the afm that turns on the fuel pump after the car is started. Try jumpering the yellow connector near the afm and see if this problem still happens.

 

It still runs, but only at high rpm. If that was the case, wouldn't it just not start?

 

It wont run at low rpm with the fuel pump connector jumpered?

Check the nuts on your throttle body elbow and the clmaps on the pipe going to the afm, check the BAC hose that goes to the air pipe, make sure the block off nipple is still on the air hose too.

 

I haven't jumpered it, I was saying it runs at high rpm without it being jumpered, which makes me think it's not the afm... All hoses seem to be plugged in but I haven't checked it yet, it is 3:30AM here right now, kinda dark to be working on it.

 

Anyone know what the problem could be?

bump

 

No bumps allowed in this section...

1)What year/model car
2)What has been done to the car (mentioning the intake before hand would help)

 

Okay, so it's an 87 base n/a, has cold air intake, header, cat delete, single exhaust, 6th ports wired open, and AAV block off plate. Also, no air pump, hence the wiring of the ports and no cat.

 

Is your AFM at an angle after putting your air filter on?

That'll muck with your driveability big time. Especially on an S4.

 

nope, no angle. It's sitting on a block of wood that's drilled into the metal, and zip-tied down flat. It's been banging around a bit, but not too bad. I've changed the tps once and put on a used one, which is a piece of junk. I've got a new afm and tps, so I'll try those, but if those aren't the problem, then what could I do?

Remember, it starts, revs, and dies without throttle input. I heard a relay clicking on and off when I'd take my foot off the throttle pedal the last time it drove, and then it did this crap...

 

Thats gotta be one loud relay......

Have you checked the AFM and TPS for clean voltage sweeps?

Also, it wouldn't hurt to do some regular maintenance items such as plugs.

 

Yeah, I think its the one under the steering column. the ones under the hood are working as far as I know, the relay still moves the plungers, so I'm assuming it works. I just changed the plugs and know the wires are good, it was running and then just wouldn't start... Very odd...

 

So could it be the relay in the car, or the tps?

 

I would definately try the AFM

The point that classicauto is trying to make is that the fuel pump only runs when there is air flow through the AFM. The engine will start fine because of the priming pulse (the ECU operates the fuel pump a little just before startup.)

At low speeds, it seems that the AFM is not turning on the fuel pump IE: the jumper wire in the connector in front of the right hand shock tower (bypasses the AFM switch.)

 

Wait wait wait, I thought the car ran but wouldn't run well at low speeds - thats what the first description says.

Now it just doesn't start?

You're going to need to be a little more descriptive please.

 

maybe it could be a vac line? i sorta had the same problem before.. one of my vac lines broke and it would start up rev high.. then die... but if i give throttle it would stay up and running.. till i let off..

 

I got it fixed, I found a hole in the underside of the CAI hose where I couldn't see, after the AFM. It made the AFM not open far enough to supply enough fuel to make it run. So I guess you could say it was the AFM, but in reality it was a leak. It wasn't something anyone would've noticed, either, since the hole was tucked away where I had to remove it just to even begin to notice. Then it became more and more clear as I inspected. After an hour I found all the problem spots. Gotta love silicone hose!

BTW, It was running one day and not the next, it would just start on the priming charge, and then die out, unless under extremely high load, where it could open the AFM completely. It would just start, rev, and die. Oh well. Live and learn. Thanks for all the help everyone, you pointed me to all of my problem spots with this thread, and I have a pretty sound runnning car. Thanks again!