Topic: E30 325i Problem

Starts okay, then runs fine until it warms up a bit, then throttle gets strange, will die at partial throttle, but rev up intermittently at WOT. It's drivable if I constantly work the throttle pedal. Last time I had these symptoms on a car I replaced the carburetor, but I can't find the carburetor on a 325i.

I'm thinking TPS, but I know nothing of E30's. Any advice would be appreciated.

Thanks

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Re: E30 325i Problem

Guessing that it's a ground on your generator.

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Re: E30 325i Problem

Fuel pressure. Intake leak. Water in electrical connector under intake. Unplug  tps. Fubar dme.

Choose your own adventure.  Good luck!

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4 (edited by TeamDFL 2018-11-14 11:48 AM)

Re: E30 325i Problem

All the above stuff plus coolant temp sensor, oxygen sensor, and/or air flow meter

Find someone with a working 325i of the same vintage and start swapping parts between the two.

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Re: E30 325i Problem

Diagnose before throwing parts at it.  Check TPS and CPS and Coolant sensor with DVM.  All the above mentioned items are common issues, also check your main ground wire from the engine mount to the body.  As the get old they cause issues.

Re: E30 325i Problem

Red Lemons Racing wrote:

also check your main ground wire from the engine mount to the body.  As the get old they cause issues.

Is this similar to Volvo Mercedes issues where the crimp on the engine side fails "internally" where corrosion and vibration have completely disconnect the wire but on rev'ing the engine it will intermitently contact.  On both the vehicles mentioned the failure is hidden by a heat shrink ID label with the part number.

If so...just replace the damn wire because it takes hours to diagnose.

Re: E30 325i Problem

Yes it is the wire rots from inside to out.

Re: E30 325i Problem

Thanks for the info.

The engine-chassis ground wasn't connected when I bought it, found that after it wouldn't start after I replaced the clutch.

I actually have a spare engine and MAF from a running car sitting here. I'll check the TPS voltage, other grounds, and start swapping stuff out.

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Re: E30 325i Problem

Check the intake boot between the AFM and the TB for vacuum leaks.  Take a jumper cable and run one lead from the engine to the chassis for a ground quick test.  If the fuel pump is external take it out, lightly tap it on a cement floor input side down, and see if you get a bunch of red silt, that indicates a rusty tank.  Also, I believe there is 1 spark plug wire that goes thru a sensor and that is prone to damage but the car will run sorta good without it.

Have had a pile of these cars and honestly, when you start to apply logic and overthink it just gets frustrating.  In my experience its always been bad ground, vacuum leak or bad/clogged fuel pumps.

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Re: E30 325i Problem

So if the TPS is full of filthy motor oil, is that bad?

Everybody grab your brooms, it's shenanigans!

Re: E30 325i Problem

Well ... yeah, a pretty good sign. But I think I would start looking for the source of the motor oil. Exhaust valve stem seals pushing oil through PVC or valve cover hose attached to plenum before the TB??

Re: E30 325i Problem

So grounds are all good now, and plugs are all connected and look good.

This thing doesn't have a real TPS, just a couple of sets of contacts that tell it if it's at WOT or idle. Those work fine.

Fuel pump and filter have been replaced.

Boots and rubber hoses look okay, but ordered new ones because they are cheap.

Tomorrow I'll try the MAF and FPR.

Everybody grab your brooms, it's shenanigans!

Re: E30 325i Problem

I'm guessing the TPS gets full of oil from the PCV system that vents crankcase air right next to the throttle shaft. Given that it doesn't have a real TPS, I'm guessing that some oil in it may only make it work better.

Everybody grab your brooms, it's shenanigans!

Re: E30 325i Problem

The vane type air flow meters are essentially a pot connected to the flapper door.  When the pot track wears out, you get crappy air measurement and crappy performance.  I have heard urban legends about tweaking/bending the arm on the pot so it contacts a slightly different spot on the board.  Welcome to the world of crappy 80s German technology.

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Re: E30 325i Problem

So replacing the FPR did nothing, but putting another MAF on it changed the symptoms. It still sputters at part throttle, but not as badly, and WOT works really well, better than it ever did before. After I hooned around town at WOT until I hit a bump and the zip ties holding the oil cooler on the car broke and it dragged under the oil pan putting a nice hole in it, it now leaks a little oil. I'm headed out to Monterey for a few weeks for work, so this may have to wait until later. I'll order a refurb MAF for it and start looking at other stuff.

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Re: E30 325i Problem

rmcdaniels wrote:

So replacing the FPR did nothing, but putting another MAF on it changed the symptoms. It still sputters at part throttle, but not as badly, and WOT works really well, better than it ever did before..... I'll order a refurb MAF for it and start looking at other stuff.

There is no such thing as a good used AFM.  You are on th eright track.  Unfortunately, reman AFMs cost a major organ from Bosch so the aftermarket remans are priced just below a kidney.

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Re: E30 325i Problem

IF it turns out to be the AFM  you could look on R3VLimited.com for a Split second or a Miller Performance conversion kit which do make the the engine run much smoother.

Re: E30 325i Problem

Thanks, the Miller kit looks really nice. I'm out in Monterey for a few weeks, so I'll have to tinker with it when I get back home.

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Re: E30 325i Problem

Just thinking out loud.
What kind of Idle Air controller does it use?  If it's the old bi-metal ones they have a tendency to break or wear out enough that they don't seal, causing a massive air leak.  When the engine heats up the fuel map changes, and bam, shitty running.  WOT doesn't care, it just tries to through all the fuel at it.

Also, change over to megasquirt.

Re: E30 325i Problem

I'll check out the IACV.

It would be nice to get a decent speed/density EMS with usable diagnostic outputs on the car. Troubleshooting this ancient crap is annoying. I also wouldn't mind getting rid of my distributor.

Everybody grab your brooms, it's shenanigans!

Re: E30 325i Problem

don't bother with the miller maf, the hardware is sketchy, the motor never runs right, and brody miller is an ass.


your car runs fine while it's in open loop on the fixed map from the ECU. it wigs out when it enters closed loop and tries to use the O2 sensor to calculate mixture. in my experience this happens because of a couple common things:
- bad o2 sensor
- bad o2 sensor wiring (check resistance from the ECU plug to the sensor plug)
- vacuum leaks (check vacuum at idle from a tee)

if those all check out, there's other more complex stuff that can be happening.

22 (edited by dmitriy 2018-12-04 05:37 PM)

Re: E30 325i Problem

also you don't have a distributor, you have a distributor cap. people convert to COP on these sometimes, but it's almost never a significant improvement over the existing (nice, made by bosch, used on many tens millions of cars) system.

Re: E30 325i Problem

dmitriy wrote:

also you don't have a distributor, you have a distributor cap. people convert to COP on these sometimes, but it's almost never a significant improvement over the existing (nice, made by bosch, used on many tens millions of cars) system.

So no hall sensor in the dizzy?  It is a true Crank position system ala EZK##?

Re: E30 325i Problem

Thanks, that makes sense. I haven't run a track car in closed loop in over ten years, so that one never occurred to me.

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