2.7i rough idle and intermittent hard starting

[e30jake]

+1

c191 plug can get corroded and cause all kinds of weird symptoms that can mimic multiple issues. Worst of all, it can be intermitent making it harder to diagnose. It's directly under the intake, round plug that screws together. There have been a few recent threads on this topic. Search for c191 and look at threads within the last month.

I actually tried cleaning the c191 plug before with some wd40 but it was hard to get inside. My threads are messed up which makes it hard to plug and unplug it repeatedly. Maybe ill just pick up an extra injector harness at the yard. Anyone know if the early and late injector harnesses are the same?

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[e30jake]

Replaced this hose today. Not sure if it actually helped or if it was a placebo effect, but it did seem a little better. It hasn't started hard since I last posted. I have had the CEL come on for 1 or 2 seconds every once in a while when I am driving, but it immediately goes back off. I also still have the problem of the idle dropping to ~500 rpm sometimes when I come off the gas or put the clutch in before settling back to around 750 rpm. It definitely seems worse when the car is cold, almost sounding like it is about to die completely. It did this even before I did the head gasket and head swap, which narrows it down to something I re-used. Would a dirty ICV cause this? All electronics tested fine from the ECU plug according to the Bentley tests other than the TPS at full throttle, which wouldn't be related to my idle. Still need to get around to doing DIY smoke test, but I'll keep screwing around with it and seeing if anything changes until then.

[e30jake]

Finally did a homemade smoke test. Was leaking a lot from one of the elbows on the throttle body that connects to the hose to the brake booster. It was the only place I could really tell smoke was coming out of due to the wind blowing it everywhere. Sealed it up and went for a drive today and it feels good. I also may have fixed the idle dip by adjusting the throttle plate, although it could have just been that the car warmed up. It feels good, but it still doesn't sound great. If I put my hand by the exhaust I can feel intermittent puffs of air, rather than a steady flow. Is this somewhat normal? I have also checked 2 of my friend's e30s. The 86 e was similar to mine, with little puffs hitting your hand. It has been driven like this for years. The 90 i was a smooth air flow, which leads me to believe my car could be running smoother. Anyone have any input on this?

[david2991]

I just finished the 2.7i install and I am having the exact same issue. I replaced all gaskets and intake components which leads me to believe I should be looking at a fuel issue. Maybe the injector or fuel regulator or pump. Either way...subscribed. Let ya know if I diagnose it.

[SmokeE30]

My car seems to idle a bit rougher after going 2.7i but I'm pretty sure it's just vacuum leaks. A lot of stuff gets disturbed durring the swap I have no doubt that something won't seal right and will require attention after a heat cycle or two on most peoples cars. Heck the first one I ever built with a buddy back in college picked up 8 in of vacuum just from retorqueing the intake manifold bolts after a couple drives.

[dumpski88]

My car won't idle after the 2.7i swap but runs fine I have seta bottom and an I head with I injectors and intake manifold and I maf but I did put some cheap headers on and It didn't have a spot for the o2 sensor so that could be the problem.