revs drop, car jerks, been searching for 2 weeks

[TopOfTheLine89]

So for 2 weeks i have attempted to solve my problem without starting a thread about it. I have ran out of ideas and would like some fresh ones.

Symptoms: car cuts out temporarily upon acceleration or idle, rpm drops for a split second but come back. This makes the car jerk a ton. I have searched and found a few threads about it but no one ever posts how they fixed it, and when they did i tried the same on mine to no avail.

I'm just looking for fresh ideas.

My car: 325e, i cam and valve springs, motronic 1.3 upgrade, intake, basically its an i now except slower :( only ran a 16.8 1/4 mile WTF?) 133k miles.

What I have done.

Checked fuel pressure,Replaced fuel filter. checked all sensors that affect the way the car runs except AFM, cleaned afm with carb cleaner, cleaned ICV, REplaced computer. Made sure al connections i could remember work. Searched the forums for 2 weeks. Tighened all terminals.

The CPS read 492 ohms and it is supposed to be 500-800 but i assumed it would be alright.

The car ran great for a week after the motronic 1.1/1.3 swap. Took it to the track, ran a few slow 16.8's (WTF) drove it home, it ran just fine. Very next morning it started acting up with the jerking and carrying on.

Im starting to think e30's are not as reliable as everyone says unless this is somehow my fault but damn. BTW I AM NO NEWB TO CARS OR MECHANICS, i am a proffesional mechanic but i have limited knowledge of electronic troubleshooting.

Thanks in advance for your expirience and ideas. Sorry for writing you all a book but i figure the more details the better.

[Adrian_Visser]

forgive my ignorance but couldn't it be a clogged fuel filter?

[TopOfTheLine89]

Checked fuel pressure and replaced fuel filter, sorry i left that out.

[Devil Inc]

Possible loose electrical, check coil, grounds. I had loose coil leads, caused my car to do weird stuff.

[Inoka]

I had similar problems that at first I thought was caused from a miss fire. Turned out to be the crank sensor shorting out.
"checked all sensors" <- probably included the crank sensor..

[Kerrath]

Checked your fuel pump? Could be a bad connection or maybe your pump is failing. It could seize when hot and once it cools down a tad pick it up again.

My friend's car kinda is having a similar problem. It stalls occasionally without good reason, even while driving freeway or at idle. We think it's his fuel pump and since he's running megasquirt in prep for being turbo'd it's not likely an afm problem or most other things related to the ECU.

Cleaned your injectors' pintles or replaced the injectors themselves?

Things I think are most likely...

[jlevie]

By "drop in rpm" do you mean that the tach shows a large drop in rpm, much more so than the actual drop in engine speed? That would tend to point to a problem with the CPS or DME, but I have seen a bad AFM produce a similar hiccup.

[E30_fiend]

Cleaning the AFM doesn't really mean you cleaned the internals. The AFM may still be the problem. I had a similar problem and I changed out the AFM and all was good.

And just to be safe, change that CPS.

Other than that I can't think of anything that would be causing those symptoms.







Taylor

[TopOfTheLine89]

Ok, maybe i will try an afm next, idk if this matters but when i unplug the AFM the problem continues. I had a loose coil wire but i tighened it which helped alot but it still jerks and gives me the original problem. And yes i checked the CPS and it read 492 ohms. The DME is good because i just bought it thinking that was the problem.

[TopOfTheLine89]

Went out to work with it tonight, found a crack in CPS wire, took the sensor off to patch it, put it back on and it hardly ran, felt like 2 cylinders. So maybe the wires are corroded or brittle.

[SpecM]

Went out to work with it tonight, found a crack in CPS wire, took the sensor off to patch it, put it back on and it hardly ran, felt like 2 cylinders. So maybe the wires are corroded or brittle.

good you got it

[TopOfTheLine89]

good you got it

Not yet, could be coincidental.

[Knockenwelle]

I've got a similar problem. Just started last night. I was driving home, and the car started cutting out. Just for a split second, like TOTL's car, but I know it's something in the ignition (switch) circuitry, cause the headlights were flicking off in unison. I jiggled the key switch, which did nothing. It got worse, then developed a pattern of about 1 second. The check computer reset (made me push the button to clear pesky lic. plate indicator) after each hiccup. Then it went away, after I angrilly yelled and called the car rude names. WTF? I'm fairly new to E30s, but I've been doing cars forever, and I'm pretty handy at electronics. I know this is either a contact issue, or computer related somehow, due to the regular pattern. Where should I start looking? TIA

Oh, and sorry for the partial thread jack...

[jlevie]

That sounds like an intermittent in the primary power circuits. The first thing I'd say to check would be the connections at the battery and at the main splice block in the engine bay

[e30serg]

I had a problem that was similar. My car would be running great, then all of the sudden, no matter how much I pushed the gas pedal down, the car would not accelerate and slowly lose power. Most of the time, the power would all of the sudden come back, making the whole car jump forward, since I had been pressing down on the gas pedal.

I noticed that it would sometimes lose power when bouncing over bumps (stiff springs don't help) and sometimes it would just happen randomly.

I checked my cps and it was fine. I didn't have much time to diagnose it, so I took it to the mechanic, who told me it was the main relay and changed it. Well, wtf, it still did it a few weeks later. I changed the fuel pump relay and it still did it. I changed the fuel pump, fuel filter, fuel lines, no fix.

I finally starting wacking whatever connections I could find in the engine bay using a screwdriver handle. I noticed that when I wacked the little cover that goes over the main and fuel relay, the idle would change and the car would stumble.

I ended up taking the main and fuel relays out, spraying the contacts with cleaner, and putting a little dab of dielectric grease into each set of connectors, and then cleaning the relays and putting them back in.

No problems since, it's been about 2 months. I've driven the same as before it happened, and it's been cool.

Sorry for the long post. Good luck!