Car hits a rev limiter at weird times and RPMs...??

[Moto-Mucci]

Just picked up an 89 325iS a few weeks ago. Previous owner told me it's got the Dinan chip in it.

I took it around town for a few hard pulls, on the highway too. It would hit what felt like a rev limiter...only it wasn't a consistent RPM. I thought the Dinan chip limited it at around 6700RPM. It was cutting off at around 5200 every now and then...then one time at around 4500. On the highway, it also felt like the power wasn't really getting to the road - reving high and not really felling like it was pulling to it's potential.

Anyone know what the deal is?

[jlevie]

I'd hazard a guess that what you are experiencing isn't the rev limiter. It is more likely that there's a problem with fuel delivery, spark, or timing reference data to the DME.

[Philo]

Definitely not the rev limiter. My money's on a fuel problem, but then agin i'm broke. Do the checks in the bentley manual before you buy anything. check fuel delivery rate at the rail. check fuel pressure regulator. there are multiple things it could be though.

[Moto-Mucci]

I know the car's got an adjustable FPR on it that's relatively new.... which leaves me skeptical. The plugs and wires are also relatively new I believe. I'll have to check the records.

It also seems to not be firing all cylinders when it's running cold - feels like a crapped coil, only it's not wet out when it does it. Once it warms up it runs fine, with the exception of the initial problem I listed. This may be a different issue though, considering this feels like one or two cylinders not firing - and the high reving issue is an all cylinder shut off.

I still have to pick up a Bentley. I was hoping I wouldn't have to so soon...

[morningsmiler]

I would run through a basic tune up and filters. While in there, look for vacumn leaks and clean connections. This way you have a good baseline to start troubleshooting from. Plus a litttle TLC in the engine bay works wonders!

[Moto-Mucci]

Yea, I was planning on doing this soon since I just picked up the car and don't really trust what previous owners say they did or didn't do.

What sucks is I live in the city and park on the street. Wrenching on the side of a busy street in the winter while buses wizz by really gets your adrenaline going...

[shiftbmw]

Were you going around turns with a low tank of gas? E30's(well my M3's at least) have some fuel starvation issues when cornering hard with very little gas and the symptoms match what your describe.

[Moto-Mucci]

nope. it's not biased to turns.

I heard it could be the fuel filter.

[Moto-Mucci]

Do these cars cut off all cylinders when they sense the mixture is too lean?

I'm wondering if the PO set the Adj. FPR too lean to fuel efficiently at high RPMs.

[nando]

Do these cars cut off all cylinders when they sense the mixture is too lean?

I'm wondering if the PO set the Adj. FPR too lean to fuel efficiently at high RPMs.

no, they don't.

it could be a bad RPM signal if it's cutting spark - I would test the crank posistion sensor & wiring. There's a clip that holds it to the timing cover, and most people either break or lose it, so what happens is the CPS wires rub on the waterpump pulley eventually grounding out and sending a bad signal to the ECU. no crank signal, no spark..

[Moto-Mucci]

But it usually only cuts out when I've got the pedal to the floor and it's either revving high or attempting to (pulling up hill).

If a faulty wire was the case, wouldn't it cut out at any time, even at low revs?

[nando]

not neccesarily. the VR signal on the E30 is pretty strong, but the higher the RPMs the more critical a clean signal is because the pulses are shorter and closer together.

it's just a suggestion because you can test it easily enough with a multimeter, rather than throwing parts at it and hoping you've found the problem.

[Moto-Mucci]

Sounds good, thanks for the input.
Still waiting on the Bentley to arrive before I start diagnosing it.

[slo325i]

I bet it's fuel pump

[Moto-Mucci]

Yea? The way all cylinders cut off at the same time seems like it would be something electrical. It's like a dead stop of cylinders. Would a faulty fuel pump have that effect?

I ordered a new fuel filter because I was advised that it may be that...and they're only like $8