Vacuum Leak
Misfire of sorts (spark plugs, coil, injector)
Throttle body or TPS sensor
Mass air flow sensor
Hello all, I am very new to this site, but I am currently on my 4th BMW. First car was an early 90s # series, then a 1989 750il, then a 2002 x5 3.0i, now I am currently driving a 1995 BMW 740il!!
With that being said, it is my daily driver. I have recently done a LOT of work to it.
New parts:
Battery
Speakers and radio
Rewire headlights and running lights
New rear suspension, removed SLS
New front bushings
Valve cover gaskets
Spark plugs
etc
This week the car started running rough, so I pulled the valve cover gaskets to be sure the spark plugs were not submerged in oil again, and they were not. So I found a shop who had a BMW adapter to run the check engine light codes. The code that came up was p1251. Online it says something about "Cold start valve injector shorted to B+ positive". But after two days of googling, I can tell you this 4.0 v8 1995 740il does NOT have a cold start of any kind as far as I can tell. So perhaps I am misdiagnosing the P1251 code? Any ideas? Also My engine is very shakey and I am losing a lot of power as if I am having a weird misfire/limp mode.
I wonder if it is one of four things:
1. Vacuum leak anywhere
2. Bad spark plugs/injector/coil
3. Throttle Body issue
4. Mass Air Flow sensor
From what I could find online, it says throttle motor fault. The throttle in the M60 engine you have is manually controlled by cable, so there is no throttle motor, but there is a throttle position sensor, and when those go bad the engine has the symptoms you are describing. If you have a Bentley manual, there is a resistance test for the TPS to see if it’s bad. You may be able to find it online too. I would check that first.
Additionally, I may be wrong, but I think the M60 is an OBD1 engine, so you may not be able to use a standard OBD2 reader to get accurate codes. Google and read about the Stomp Test for BMW OBD1 cars. That may yield an accurate code. Videos on YouTube will show you the test.
Last edited by kouks; 12-04-2017 at 10:36 PM.
02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)
My local advance auto and my local autozone dont have manuals or bentley books telling me how to test the TPS. Also if i replace it i imagine i would have to calibrate it. Does anybody have a manual they could photocopy and load on here? I just pulled the intake manifold and injectors to clean everything. The timing is perfect. I have easy access to the TPS.
This car does not have obd2 port for my tool. I removed the plate at the bottom left hand side of the ashtray on the panel with the radio. There was no port. Under the hood on the right hand side I found the round port for diagnostics. I ordered the adapter from China. I am still waiting for it. But I have completed the stomp test and it gives me code P1251.
As I stated before it seems this is a cold start valve code. But my car is fuel injected, it does not have a carb. I followed the fuel rail and there only seems to be 8 injectors. No cold start injector.
So if it is indeed the TPS, does anybody have a manual with direction on how to test the sensor with a multimeter? Id like to establish if its a wiring issue or sensor issue, IF this is the culprit. THANKS FRIENDS and happy holidays
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