Car is hesitating when accelerating?

[E30_Narek]

So for the past... 8 or so months my car's been having this problem and it seems to be getting worse. It has a really rough idle when started while warm, gets terrible MPG (I'm talking like 13-15) and has a slight hiccup when I accelerate. Also, it feels like it's lacking some power. I took it to a mechanic and he said it's the ICV but after doing some tests I've read online, I'm sure it's not the ICV. It's not the AFM either because I tried out a new AFM on the car and the problem persisted. I've narrowed down my problem to either the O2 sensor or the TPS. Could anyone else shed some light on this please?

[dnguyen1963]

I would make sure that you have no vacuum leaks when the engine is warm before doing anything else.

[Kershaw]

Definitely check for vacuum leaks. If you unplug the afm, does it run differently?

[itsonlygeorge]

Vacuum leaks first - check all rubber hoses starting with the intake boot and pretty much all the lines under the manifold. If it looks cracked, replace it. Check around the hose clamps, most cheap clamps will dig into the rubber and eventually it will crack or tear. Wiggle the hoses to find cracks. You can try tape any cracks temporarily with electrical tape so see if that improves your idle.

If you have a leak no amount of tweaking the ICV will help, trust me I tried. Set the ICV so the idle is at ~750 rmp once the car has warmed up to temp.

Check the O2 sensor - I had a shitty idle and stuttering even when warm when I had a bad sensor. Check it by unplugging the sensor harness in the engine bay (it's on the passenger side near the strut tower). This will force the ECU to use the stock fuel maps instead of real-time data from the O2 sensor. I ran my car like that all winter and it was fine.

You can get a Mustang O2 sensor for $10 and splice it in. The only difference is the plug so save the old one!

http://www.unofficialbmw.com/phpBB/v...ic.php?t=30763

Here's what I used: Bosch 13913 Mustang O2 Sensor (For $10 you can't really go wrong. Just cut the connector off and crimp it to your old harness and you're done!)
http://www.ebay.com/itm/NEW-BOSCH-OX...BTwM7d&vxp=mtr

More expensive but pretty much the same: Bosch 13942
http://www.ebay.com/itm/BRAND-NEW-BO...FVrqmF&vxp=mtr

[E30_Narek]

I would make sure that you have no vacuum leaks when the engine is warm before doing anything else.

I've got no vacuum leaks, mechanic smoke tested it but couldn't really figure out the problem.

Definitely check for vacuum leaks. If you unplug the afm, does it run differently?

No vacuum leaks. If I unplug the AFM the car stalls.

Vacuum leaks first - check all rubber hoses starting with the intake boot and pretty much all the lines under the manifold. If it looks cracked, replace it. Check around the hose clamps, most cheap clamps will dig into the rubber and eventually it will crack or tear. Wiggle the hoses to find cracks. You can try tape any cracks temporarily with electrical tape so see if that improves your idle.

If you have a leak no amount of tweaking the ICV will help, trust me I tried. Set the ICV so the idle is at ~750 rmp once the car has warmed up to temp.

Check the O2 sensor - I had a shitty idle and stuttering even when warm when I had a bad sensor. Check it by unplugging the sensor harness in the engine bay (it's on the passenger side near the strut tower). This will force the ECU to use the stock fuel maps instead of real-time data from the O2 sensor. I ran my car like that all winter and it was fine.

You can get a Mustang O2 sensor for $10 and splice it in. The only difference is the plug so save the old one!

http://www.unofficialbmw.com/phpBB/v...ic.php?t=30763

Here's what I used: Bosch 13913 Mustang O2 Sensor (For $10 you can't really go wrong. Just cut the connector off and crimp it to your old harness and you're done!)
http://www.ebay.com/itm/NEW-BOSCH-OX...BTwM7d&vxp=mtr

More expensive but pretty much the same: Bosch 13942
http://www.ebay.com/itm/BRAND-NEW-BO...FVrqmF&vxp=mtr

I've got absolutely no vacuum leaks. I've already ordered an O2 sensor from BMA and should be picking it up later today. Didn't want to get a mustang one because I might as well get an OEM one. I don't really want to drive around with an unplugged O2 sensor because I want to improve my MPG. The car will run rich if it's unplugged so I'll end up using even more fuel.

[itsonlygeorge]

Car is hesitating when accelerating?

Did you try unplugging it and driving the car? The car shouldn't run rich with the O2 unplugged. You can test it to see if the O2 is the culprit.


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[Kershaw]

An m20 shouldn't stall with just the afm unplugged.

Have you tested your injectors? Maybe they're leaking. Can you swap your dme with anyone?

[E30_Narek]

Did you try unplugging it and driving the car? The car shouldn't run rich with the O2 unplugged. You can test it to see if the O2 is the culprit.


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I'll try that. I only said it'll run rich because that's what I've read other places.

An m20 shouldn't stall with just the afm unplugged.

Have you tested your injectors? Maybe they're leaking. Can you swap your dme with anyone?

Never tested injectors but when I took it to the mechanic to have it smoke tested he said there's nothing wrong with the injectors and they're all getting spark. I unplugged the AFM while my idle was rough so that's probably why it stalled. And no, I can't swap the DME with anyone. Don't know anyone else with an E30. My only friend with an E30 sold his a while ago.

[E30_Narek]

I should add that at one point my check engine light was on. It threw the code 1221 which is the O2 sensor. It's gone now and even when I do the stomp test I get the code 1444 (no faults).

[E30_Narek]

UPDATE: Today I changed the two temperature sensor on the thermostat and the fuel filter. I changed the fuel filter a couple months ago when my car was running terrible and that seemed to fix the problem but I still had the problem I am having now. So while I was changing the fuel filter I realized I put the fuel filter on the wrong way... Hopefully that's what was causing all my problems but nonetheless, I will change the oxygen sensor tomorrow.

[scuddyholly]

So is it running better now that you switched the fuel filter around. Was there any fuel in those lines when you pulled them apart?

Fuel filter or regulator?

I'm trying to track down a vacuum leak that just keeps getting worse. If I don't have the A/C running on a cold start it dies. However idles perfectly with the ac on.

I've changed a few hoses, cleaned the icv, but haven't done a smoke test yet.

[E30_Narek]

So is it running better now that you switched the fuel filter around. Was there any fuel in those lines when you pulled them apart?

Fuel filter or regulator?

I'm trying to track down a vacuum leak that just keeps getting worse. If I don't have the A/C running on a cold start it dies. However idles perfectly with the ac on.

I've changed a few hoses, cleaned the icv, but haven't done a smoke test yet.

Nope, car doesn't drive any different. There was fuel in the hoses. I changed my O2 sensor yesterday and it's still doing the same shit.

I'm starting to think my car has a vacuum leak. Even though my mechanic said he smoke tested it, I don't really believe him at this point because he also claimed the ICV was bad but didn't even do the tests to check it which I did and the ICV does in fact work. I'm going to start changing all my intake gaskets and vacuum hoses. Hopefully that'll fix it.

[scuddyholly]

Yeah I changed my o2 with no change as well.

I've been told if its not the ICV or any of the hoses, that its commonly a leak by the throttle body. Mine looks pretty gunky and I am fairly sure the gaskets need to be replaced. I began to remove the hoses but one of them is a coolant line and it started spraying coolant everywhere, haha. I guess I will have to flush the coolant before I attempt it again.

Also it might not hurt to replace the intake boot they like $20 and another common culprit for a leak.

[E30_Narek]

Yeah I changed my o2 with no change as well.

I've been told if its not the ICV or any of the hoses, that its commonly a leak by the throttle body. Mine looks pretty gunky and I am fairly sure the gaskets need to be replaced. I began to remove the hoses but one of them is a coolant line and it started spraying coolant everywhere, haha. I guess I will have to flush the coolant before I attempt it again.

Also it might not hurt to replace the intake boot they like $20 and another common culprit for a leak.

I changed my intake boot like a year ago, it had a few cracks in it haha. I doubt it's the ICV though. It wouldn't give problems upon acceleration.

[JeLani]

inline fuel pump? this caused mine to even act like its running out of gas. before I replaced mine it would lose power at high rpm and I would have to tap the pedal .