Rough idle at cold start/stop

[shameson]

So after spending some time off the road, was able to get my e30 running again about 2 weeks ago. The m42 had its hoses replaced along with numerous other parts during that time. The only issue I'm having now is during cold starts, the idle will bounce a little for a few seconds normally at startup, then level off and idle where it should ~750-800. If it start it up and pull away, when I'm come to a stop at the end of my street, once I push in the clutch to stop the idle will bounce low to point it feels like it almost wants to stall and cause slight shaking, like ~500-550 rpms.

After a minute or two there is no issue and car will idle and stop just fine. Prior to my car being off the road for 3 months, it never did this. During the time things like the fuel filter, fuel pressure regulator, hoses and vacuum lines, oxygen sensor, etc. we're replaced. And ICV was cleaned.

One thing I know that can cause this is worn valve seals allowing a little oil into the combustion chamber, but I'm not sure I believe that's the culprit yet. Any other ideas?

[roguetoaster]

My car did a similar thing on several occasions, the first time it was the O2 sensor (probably not your issue, and it was intermittently flashing the CEL), the second it was a partially/later fully disconnected wire at the TPS connector. However, the latter occurrence did happen no matter the engine temperature if I remember correctly.

[Dj Buttchug]

hmmmmm

[shameson]

My car did a similar thing on several occasions, the first time it was the O2 sensor (probably not your issue, and it was intermittently flashing the CEL), the second it was a partially/later fully disconnected wire at the TPS connector. However, the latter occurrence did happen no matter the engine temperature if I remember correctly.

Ya O2 sensor is new, but I may try putting the old one in just to see what happens. I believe I still have it. And I'll check my connection at the tps, make sure it's good since I've had it off a few times

hmmmmm

Me too

[groupus]

The idle bouncing may be caused by a dirty icv, did that on my old 325. You migh have knocked some junk loose. My new 318is has been having a similar type of issue this winter - from dead cold it will run fine until it warms up just enough to move the needle, then it will idle very low and lopey, almost stalling or missing, and it's lacking power under 2k rpm. Once it warms up above the second mark its fine again. The car sat before I bought it in August, but ran fine after some maintenance - mess under the intake, intake boot, air and fuel filters, spark plugs, cleaned injector and new seals, upper/lower intake gaskets, oil filter housing gasket, TPS, and a thorough cleaning.

After this issue started, I replaced the O2 sensor and played with the wire related to the hot/cold start issue but that didn't change anything either. Most recently, I changed the temp sensor which also didn't fix it, but the car then didn't start one day. Swapped back to the old one and it worked for a few days but wouldn't start again. I bought another new sensor and the same thing is happening.

Sorry if mine doesn't sound exactly the same, but it did start out similar. It's really annoying and takes the fun out of driving the car. And now I have to carry around an extra temp sensor because I can't trust it to start. I suggest you start by cleaning the icv again and do the stomp test to check for codes ( I now get 1222 for O2 sensor reading too rich/lean). Other people usually suggest checking for vac leaks, but since you've replaced vac hoses like me, it's probably something electrical related to temperature. Try disconnecting the temp sensor or AFM when it starts acting up to see if that . Also, clear the codes after replacing sensors by disconnecting the battery so that it can reset if it was stuck in open loop mode.
I keep searching but have not found a solution yet. I will update as I keep testing other options.

[shameson]

Ya I still have all my old sensors so I'll just work backwards on my car again, just to see if anything changes. Try my previous O2 and temp sensor just to be sure. I'm not sure the icv would cause this but I will be replacing it with a new one in the future regardless

I'll do some testing and such. Run a stomp test and see what it comes up with

[Dj Buttchug]

post a video of what happens when you get a chance

[shameson]

I'll try to get one in the morning before work

[MX339]

Make sure you didn't plug in the connector for the Catalytic Converter signal bypass. When I swapped in my E36 M42 I unknowingly connected it and was chasing a rough running problem at start up for quite some time. Your issue does sound a wee bit different than mine though, mine was mostly a hot start issue.

[Cosmic Serpent]

this might not solve the problem, but after id did my o2 i still had a bit of the same idle issue. So i checked the hoses my issues seemed to be oil build up in the hose from the fuel pressure regulator to the throttle body. so i pulled it off the FPR and blew through it seemed to fix the problem.
it might of been a coincidence but it fixed the problem.
so it might be worth doing.

[shameson]

Make sure you didn't plug in the connector for the Catalytic Converter signal bypass. When I swapped in my E36 M42 I unknowingly connected it and was chasing a rough running problem at start up for quite some time. Your issue does sound a wee bit different than mine though, mine was mostly a hot start issue.

It definitely isn't plugged. I've have the harness cover in the last couple months. Wish it was that simple lol

this might not solve the problem, but after id did my o2 i still had a bit of the same idle issue. So i checked the hoses my issues seemed to be oil build up in the hose from the fuel pressure regulator to the throttle body. so i pulled it off the FPR and blew through it seemed to fix the problem.
it might of been a coincidence but it fixed the problem.
so it might be worth doing.

I changed the fpr and the vacuum hose for it during the the time off the road, so it might but worth checking that to make sure its not doing that

Probably won't be Friday/Saturday until I can really dig into some of these ideas. But I will try to take a few minutes to get a video before I leave work in the morning

[groupus]

I plan on replacing my valve cover gasket soon. I have oil around my spark plugs, so this could definitely cause a vacuum leak when cold. I'm just waiting for a helicoil kit to come in the mail. The PO took it to pep boys and they stripped a few of the bolts out.

[shameson]

I plan on replacing my valve cover gasket soon. I have oil around my spark plugs, so this could definitely cause a vacuum leak when cold. I'm just waiting for a helicoil kit to come in the mail. The PO took it to pep boys and they stripped a few of the bolts out.

I did my vcg over the period but that's interesting cause there was one spot where it appeared oil was leaking through...I forgot that could a vacuum leak. I was positive it was bolted to spec but maybe I should double check the torque since I now have a better torque wrench. Or just redo it altogether

[groupus]

Just an update: I replaced my VC gasket with no change. It still has a very annoying and persistent "missiness" between 0 and the first mark on the temp gauge. My next thought is something electrical like the coils/wires or a bad solder joint on the DME. There could be a bad connection that gets closed as components heat and expand. I'll pull the computer out and look at it. I've also been thinking of doing a COP conversion and I recently found someone selling the coils from a 540.

[shameson]

Just an update: I replaced my VC gasket with no change. It still has a very annoying and persistent "missiness" between 0 and the first mark on the temp gauge. My next thought is something electrical like the coils/wires or a bad solder joint on the DME. There could be a bad connection that gets closed as components heat and expand. I'll pull the computer out and look at it. I've also been thinking of doing a COP conversion and I recently found someone selling the coils from a 540.

My coils are only a couple months old and the sp wires have been replaced at some point too. I found it odd the that in the last week and half it didn't do it. Then yesterday morning after starting it up to head to work, it did. Does seem that it's almost a little worse when I stop on a decline, but I've had it not do it at all in the same location the week prior so it's not consistent.

A friend and PO of the car recommend replacing the ICV, as he had a very similar issue with his own m42 car and that was it, so that's my next step. Going to order a new one this weekend and see if that clears up the issue. I still want to get a short video but every time I tried it wouldn't do it lol.