Need to exterminate a Gremlin (HELP)

[sennafan]

Problem: When I get my car (88 325is with MarkD and mustang injectors) between 3 and 4k it feels like it has hit the rev limit. It will also cut power sometimes. It is really bad when I try to autox the car. I know its not fuel starve because I have the tank full.

What I have replaced so far: ecu, fuel pump, fuel filter, wires, cap and rotor, temp sensor, afm.

I have checked all the grounds that I can find. I don’t have a catalytic converter on the car. I am going to change the fuel rail back to stock with stock injectors.

ANY SUGGESTIONS? THANKS.

[Myster-E]

get rid of the mark d chip. done

[sennafan]

get rid of the mark d chip. done

Going to try that soon. Waiting on a set of stock injectors.

[MR 325]

I prefer a nice ebay chip and M50 injectors.

[sennafan]

Today I individually replaced:
AFM
TPS
fuel rail
fuel pressure reg
went back to stock ecu and injectors

NO Freeking change

[jlevie]

Is this happening above 5k? Check the WOT switch in the TPS.

[sennafan]

Is this happening above 5k? Check the WOT switch in the TPS.

Its happening between 3 and 4k. If feels like I am hitting the rev limiter.

[jlevie]

That would make me suspect the AFM or DME if the engine performs normally above and below that speed range. However, if the engine won't go above 4k, I'd suspect a fuel deleivery problem, bad CPS, or a bad DME.

[matt0300]

Ill trade u a stock set of injectors and stock dme with used cps(working) for ur marks chip.

[sennafan]

Another wasted day working on this POS! Today I replaced the coil, fuel pump and bought and replaced another fuel filter.

The problem is really weird. It happens between shifts. If you make a rolling stop and take off in 2nd it studders, then it studders between all shifts. If you are on the freeway cruising it runs ok.

[jlevie]

The first things I would have done would have been to smoke test the intake and check rail fuel pressure. If those were okay I'd have replaced the CPS & O2 sensor and reverted to a stock DME and injectors.

[sennafan]

The first things I would have done would have been to smoke test the intake and check rail fuel pressure. If those were okay I'd have replaced the CPS & O2 sensor and reverted to a stock DME and injectors.

I am going to pick up a cps and o2 sensor. I will have to look into a smoke test.

[sennafan]

Took my pos out today and had the same problem. I am losing pertinence with this car. The car runs good on the freeway cruising at 70mph and 2500rpm, but around town when I accelerate and have to go over 2500rpm it stalls like it hit the rev limiter. I also had an instance where the tach dropped to 0, I kept my foot in it and it coasted for approx 10 seconds and power came back.

[jlevie]

I also had an instance where the tach dropped to 0, I kept my foot in it and it coasted for approx 10 seconds and power came back.

That is a significant clue. The tach going to zero (or just dropping) while the car is in gear and moving means that the DME is loosing timing data, loosing power, or shutting down.If the DME looses power or shuts down, the CEL will come on, but no fault codes will be stored. If the DME looses power there may, or may not, be stored fault codes. And if there are fault codes they may point to a problem with the fuel pump relay or injectors, which is a red herring.

I'd replace the CPS with a new BMW (in a white box w/BMW logo) part. I'd also check the DME grounds and replace the fusible link with a 60a fuse. If the problem persists, replace the engine harness.

The easy replacement of the fusible link is to cut it out and splice that wire (with solder connections and heat shrink). Then mount a 60a lug type fuse to the power point in the engine bay between the DME power wire and the power point.

[7pilot]

I would recommend pulling the instrument cluster, cleaning the contacts for the various plugs, adding a little di-electric grease, then putting in all back together. This will rule out poor connections for the road speed and engine speed data between the i/p and the DME.

m