Rough idle and hard start...sometimes

[herbivor]

I have a 92 M50NV. O2 sensor and Air mass meter boot were recently replaced. (boot had a hole). The car has always been a little slow to start. Crank time is about 3 to 4 seconds. But yesterday after coming out of a 2 hour movie I cranked and it wouldn't start. It took about 3 long cranks (about 8 seconds each before it fired up and when it did it stalled about three times. It wouldn't hold rpm above 500. So I had to keep the revs up to get out of the parking lot. Highway driving was fine but at slower speed it was surging and chugging along . At stop lights it almost stalled bouncing below 500 a couple times until I quickly reved it a little to keep it from stalling. Engine felt a little rough. I assumed I had a slight vacuum leak and would take care of it this morning. Started the car this morning and it fired right up (after the normal 3 to 4 seconds). No rough idle or anything. Any thoughts? This has actually happened a couple times and its frustrating because it's not consistent.

[herbivor]

I should also mention the car sounds like it backfires once and awhile. It did it again today.

[mlytle64]

hi mike!
fuel pump maybe? that might also go with the lean condition on the dyno. there is an afpr in the car that was dialed up to 60psi when i got the car. i had dialed it back to 50 which is what i run my race car at. no idea age or history on the fuel pump. it could be old or the screen on the bottom could be clogging.

although i changed fuel filter, it could be clogged with fuel tank stuff since the car sat for over a year before i resurected it.

i didn't drive it much, maybe 50miles and didn't see same symptoms.

did you get the a/c working? what was the issue?

marshall

[herbivor]

Figured it all out. There was a broken tube that connects to the ICV. I guess it was pretty brittle. We also scoped the cylinder bores and tested the fuel injectors and found 1 of them leaking like hell. So now I'm in the process of replacing those. The AC evaporator coil needed to be replaced which was done. It was blowing nice and cold until about 5 minutes into my drive to Charlotte (@95 deg.) when the blower stopped working altogether. Replacing the resistor pack this weekend. Hopefully that will do it for awhile. I expect a few more parts will break in the coming months as a result of sitting for awhile. But still worth it.
My buddy just bought a 08 Honda Accord for $18k with zero options, quite possibly the most boring car in the world. I feel ok spending a few k on getting mine perfect and having a completely unique and beautiful car for half the price of what he paid.

[mlytle64]

nice! i had all that out (icv, manfold, fuel rail, injectors, etc) when i was cleaning it up and replacing the starter. possibly the old plastic tube and intake bellows got flexed too much. must run better without the extra air in the system! i would send the injectors to RCEngineering in california for blueprinting vice replacing them. they will come back in a few days and be balanced better than new with documented spray patterns. cheaper than new too! i do this for my race car.

i really love the color of that car. you are making me miss it....;)

[colorado_cabrio]

coolant temp sensor?

[herbivor]

Well, I thought I had it figured out. I threw some new injectors in and a new resistor pack in this morning. That was a waste of $500. There is apparently a short somewhere for the blower fan and I'm still having the hard start problem. After reading my E30 Bentley Manual, it sounds like a faulty cold start valve. But I don't know have the E36 Bentley manual to know if that could be the problem. Either way, I think I have to bring it into the shop because I'm tired of messing with it.

[Adrian_Visser]

Well, I thought I had it figured out. I threw some new injectors in and a new resistor pack in this morning. That was a waste of $500. There is apparently a short somewhere for the blower fan and I'm still having the hard start problem. After reading my E30 Bentley Manual, it sounds like a faulty cold start valve. But I don't know have the E36 Bentley manual to know if that could be the problem. Either way, I think I have to bring it into the shop because I'm tired of messing with it.

Cold start valves were used on early m20's brah m50's don't have one. Did you swap coolant temp sensors yet?

[mlytle64]

cold start.....two senders on side of block near front. back one is for temp gauge on cluster and it is direct wired (by me) to the temp gauge and tested sat. the front one is the sender for the ecu. it checked out fine when i tested it two months ago.

correct, m50's do not have cold start valve. the idle control valve could be sticking though.

blower. did you apply direct 12v to the wiring plug for the fan itself to make sure it ran? does fan work at all? if it only worked on high, then that is a fan resistor problem. if it does not work at all, either fuse is blown, power wire is disconnected somewhere, switch is bad, or the fan itself is dead. check for power at fan and check if fan works with 12v direct from battery.

[herbivor]

The reason we thought it was leaking fuel injectors was because we scoped the cylinder bores and then the intake manifold and found gas spraying into cylinder 5 or 6 when the fuel pressure was held on. Unfortunately, my do-it-yourself days have become severely limited when we moved to a home that doesn't have a garage and we had a kid. A day to myself comes once in a blue moon. That was this past Saturday. On to the trusty mechanic!! I'll let you know what they end up finding.