Misfire when cold after thermostat change

[blacksport325]

Hey all, recently replaced the t-stat with the same part from a old 5 series. During the install, I unbolted the fuel rail just to move it a bit, unplugged the 1st injector, and the fuel regulator(?) right above the thermostat. Now after getting it all back together it will misfire/idle rough on a cold start and when I take off it looses power, but this only happens during the first minute or so the car is on, otherwise it's fine. I looked around and couldn't find a definite answer, I replaced the switch and one of the coolant temp sensors on the thermostat thinking that may be the problem. Is there a certain way the first injector is supposed to be seated, it looks like it can twist freely with some resistance. Also could the other temp sensor I didn't replace cause this? Thanks in advance.

[NC325iC]

which one did you replace?

[blacksport325]

# 15,16 on the picture below.

[immajackuup]

blown head gasket,check spark plug for coolant.

[jlevie]

Was the cold start problem present before replacing the temperatue and time-temperature switches? If so the prime suspects would be intake leaks and/or a bad cold start valve. If the problem wasn't present before, the parts you installed might be be bad, or you may have introduced intake leaks when you disturbed the injectors. A smoke test of the intake will tell if intake leaks are present.

[blacksport325]

blown head gasket,check spark plug for coolant.

Really? I doubt that, no coolant in oil so the gasket is good.

[blacksport325]

Was the cold start problem present before replacing the temperatue and time-temperature switches? If so the prime suspects would be intake leaks and/or a bad cold start valve. If the problem wasn't present before, the parts you installed might be be bad, or you may have introduced intake leaks when you disturbed the injectors. A smoke test of the intake will tell if intake leaks are present.

No it did this right after I installed the thermostat. I'll look and see where the cold start valve is, thanks for the help.

[immajackuup]

Really? I doubt that, no coolant in oil so the gasket is good.

coolant doesn't have to be in oil to get a blown head gasket. check spark plug.

[alpineE30]

like jlevie said about air leak but I also suggest that the contacts on your injectors could be the problem cause I messed with my fuel rail once with the thermostat housing and had it misfiring like a subaru. and yeah you can twist the injectors with a little of resistance. unplug the injector wire and connect it a few times and see if it effects the misfire or press on it a little like wiggling it dont break it lol. also there is grease for electrical contacts and Id say put some on your thermostat housing sensors and on that injector dont put a lot on you only need a small dab of it.

[blacksport325]

like jlevie said about air leak but I also suggest that the contacts on your injectors could be the problem cause I messed with my fuel rail once with the thermostat housing and had it misfiring like a subaru. and yeah you can twist the injectors with a little of resistance. unplug the injector wire and connect it a few times and see if it effects the misfire or press on it a little like wiggling it dont break it lol. also there is grease for electrical contacts and Id say put some on your thermostat housing sensors and on that injector dont put a lot on you only need a small dab of it.

Good advice, I will do that this weekend. I'll probably pick up that second sensor as well. My guess is it had to be that injector as well since I've never touched it, then once I do its misfiring at startup. I'll let you know if these fix the problem.