88 325ic vs 89325is motor need help

[Tismael711]

I have a 1988 325ic automatic. I purchased it with a blown motor and quickly purchased a motor from a 1989 325is 5 speed. A local (non BMW) mechanic did the swap for me. The engine ran ok for about 1 hour, thereafter, it will start but cut off as soon as i put it in gear and try to take off. The car literally breathes.....the idle goes up and down. Local mechanic says bring it back, its probably the throttle position sensor. Others that i have talked to say its the idle control valve. Im not confident in the local mechanic. At this point i want someone with BMW experience.

I noticed that nothing is plugged into the thermostat temperature sensor. Local mechanic says it doesn't need it. I also noticed that the TPS is for a standard (5speed) car. Mine is an automatic. Is there a difference? I need some sound, experienced advice.

Ismael

[jlevie]

That sounds most like intake leaks and a sticky ICV. But a bad TPS is a possibility. A smoke test of the intake will reveal any and all intake leaks. The ICV can be removed and cleaned and if the TPS is bad it needs to be replaced. The TPS is the same for all M20B25 engines, regardless of what transmission the car has.

[Tismael711]

cold start and idle problems

I cleaned up the ICV with carb cleaner and it still would not start. However, today it started right up but idles high then low....then high again. Today it was a lot warmer than the previous days so i think it has some sort of "cold start" problem.

I purchased a new Throttle Position Sensor (TPS) and i hope that can remedy the problem. Any other thoughts since i believe the cold weather had something to do with the starting problem?

[jlevie]

Intake leaks cause a greater problem as the temperature drops. They could easily explain both the starting and idle problems.

[Kershaw]

Intake leaks cause a greater problem as the temperature drops. They could easily explain both the starting and idle problems.

you are just a wealth of knowledge. absolutely amazing. kudos to you sir.

do you think this happens because as temps rise, materials expand and small leaks get sealed?

[IRON-E]

I'm probably going to be ashamed for my suggestion but the CPS (crank position sensor) will cause similar issues as well. I replaced all kinds of things before getting to my CPS, my car's sensor was old and brittle and full of grime and dirt., after examining it there were a lot of broken wires that would give enough power for my car to start and go for about 10-15 mins and then it would take a shit.

It's just a suggestion that you should check out if all else fails you, good luck.

[-limp-]

im betting its prolly a cracked intake boot remove yours and give it a 360 look-a-round before buying anything