Hestitation in idle.

[Doughnut]

Engine is '89 m30b35, m30 harness in 89' 318i chassis.

Ever since I put the engine in the car Ive had a hesitation/stutter everytime I put my foot on the gas from idle. Ive put up with it until now.

Tried:
Replacing known working tps, icv, engine ecu temp. sender, o2 sensor is fine, injectors are rebuilt, 'o' rings replaced and there is no vacuum leaks.

Only thing I can think of left to replace is the afm and/or fpr.

What do you guys think? anyone got the same problem?

[yert315]

i adjusted my afm and it helped quite a bit. Some may think it's not a good idea to mess with the internals of it, but it's easy to go back to the "stock" locations of the wheel if need be.

[Iain]

Could also be spark plug gap and/or leads, or even the coil (do M30s even run a coilpack/s?).

Also, how's your o2 sensor?

[Doughnut]

i adjusted my afm and it helped quite a bit. Some may think it's not a good idea to mess with the internals of it, but it's easy to go back to the "stock" locations of the wheel if need be.

Do you mean the allen key (internal hex head) screw on the afm? I'm not to keen on adjusting that but I dunno...

Could also be spark plug gap and/or leads, or even the coil (do M30s even run a coilpack/s?).

Also, how's your o2 sensor?

Checked spark plugs again today (they are new and were put in not long ago) and swapped out the coil for a known good working one.
No change.

o2 sensor is new and plugged in, engine has same problem when i plug and unplug it while the engine is running.

[yert315]

Do you mean the allen key (internal hex head) screw on the afm? I'm not to keen on adjusting that but I dunno...

no, that allen bolt is more-or-less for emissions at idle (air bypasses the flapper). What I am talking about is the wheel inside the afm unit itself. You can loosen or tighten the wheel which adjusts the spring tension of the flapper on the inlet of the afm. Loosening (turning the wheel left) it will give you a richer fuel mixture throughout the rpm range and vice versa when you tighten (turn to the right). I loosened my wheel by 2 teeth and it has smoothed out the entire rpm range. Apparently m30s like to run on the lean side. Like I said, you can always go back to factory settings if it doesn't work out for you.

here is a picture of what I am referring to.

[LowR3V'in]

When you loosen the wheel you make it richer, not leaner.
My opinion is not to fuck around with the afm.

[yert315]

thats what I said.

I know many people say not to deal with the afm. I just threw it out there as an option.

[Iain]

AFM is definitely a likely suspect.

Tried swapping to a new set of ignition leads? I had a similar problem with my Liberty RS and it turned out to be a lead that was ever so slightly starting to break down internally.

[wildstoats]

I don't have anything specifically about your hesitation issue but if you do want some more info on adjusting the AFM check here:

http://www.mye28.com/viewtopic.php?t=21255

http://e28-535i.com/technical/AFM%20Repair.pdf

[Doughnut]

I don't have anything specifically about your hesitation issue but if you do want some more info on adjusting the AFM check here:

http://www.mye28.com/viewtopic.php?t=21255

http://e28-535i.com/technical/AFM%20Repair.pdf

Thanks for these links!

Thankyou to all for the very helpful info! I'll try swapping out the AFM for a known working one ASAP and get back to you guys.

[flawdaboi407]

Engine is '89 m30b35, m30 harness in 89' 318i chassis.

Ever since I put the engine in the car Ive had a hesitation/stutter everytime I put my foot on the gas from idle. Ive put up with it until now.

Tried:
Replacing known working tps, icv, engine ecu temp. sender, o2 sensor is fine, injectors are rebuilt, 'o' rings replaced and there is no vacuum leaks.

Only thing I can think of left to replace is the afm and/or fpr.

What do you guys think? anyone got the same problem?

I have the same problem.. sometimes the engine will even die and not start for a few seconds. I can smell fuel when tring to start it back up. I tried another afm, icv and adjusting the tps with no sucess. My plugs are new, injectors refurbd, no vacuum leaks, new o2, cap and rotor are good, new coil. Also tried cleaning the afm and icv... i got the sputter to go away at idle but... sometimes the engine still cuts out when i tap the gas at idle. I threw it on three different scanners at work and found nothing. My boss thinks it might be a tps going bad, or the main relay going bad. I swapped the main relay (the white one) and been driving for two days and havent had the problem yet.. seems to be heat and driving real hard related. Weird. Still trying to figure this crap out. IM SO READY FOR MS.

[FreedS4]

I have the same problem.. sometimes the engine will even die and not start for a few seconds. I can smell fuel when tring to start it back up. I tried another afm, icv and adjusting the tps with no sucess. My plugs are new, injectors refurbd, no vacuum leaks, new o2, cap and rotor are good, new coil. Also tried cleaning the afm and icv... i got the sputter to go away at idle but... sometimes the engine still cuts out when i tap the gas at idle. I threw it on three different scanners at work and found nothing. My boss thinks it might be a tps going bad, or the main relay going bad. I swapped the main relay (the white one) and been driving for two days and havent had the problem yet.. seems to be heat and driving real hard related. Weird. Still trying to figure this crap out. IM SO READY FOR MS.

Any more info on your fix for these issues? I'm having some of the same problems and can't seem to fix them.

[FreedS4]

Any more info on your fix for these issues? I'm having some of the same problems and can't seem to fix them.

My TPS wasn't reading any ohms until it hit the idle stop and sometimes didn't register ohms at all. I've adjusted it so it's reading accurately now and my idle seems a litle more stable and doesn't want to cut out when I let off the gas abrutly. The RPMs also don't drop as far down as they used to when I let off the gas. The only thing I haven't checked is the cold start-up and it's tendency to almost die at first. I'll let her cool down fully and check it out, but all signs point to it being fix, or at least better. Thanks for all of the help.

[FreedS4]

Just went and started her up and she's having the same issues as before on start up. Jumps up to 1000ish RPMs, then drops to 500ish RPMs and settles at around 600-650 RPMs. If you give it some gas and then let go, it drops to 500 RPMs or lower and almost dies. The idle seems a little more stable when she finally gets warm, but when cold, not so much.

[weaksauce]

clean your idle control valve?
look for air leaks?