Poor idle, stalling, jerky accelleration

[oelholm]

Hey everyone

I believe this is my first post. Sorry if it's a bit of a long one!

I've been a proud owner of a facelift 1987 325i with a stroker engine for about a year now. It's a wonderful little car, and buying it has been the best thing I've ever done.

That being said, she's caught some bug a few weeks ago.

Recently I adjusted the valves and it's the best she's ever run. But one day I'm driving and I feel hesitation when I get on the accelerator. It was right around my apartment block so I thought I'd tuck her in and see what happens.

A day after I try to crank her, and cranking takes 30-40 minutes before the M20 lights up. Idle seems normal for a cold start, and I drive her out the garage. I park her up at the parking lots further up to take a call, and idle drops a lot. I try to give her some throttle but it surges after jumping up in the RPMs, and I recon my TPS might be out of order again, so I pull apart the entire intake. I fixed the TPS and ICV last summer, but the fault felt somewhat like how she felt when she had TPS problems.

I plugged everything back in and cranked her. Once again it's a long time before she lights up. Idle seems normal, though, and I drive her down the road to see how the engine feels. I keep it in second gear at around 3000rpm and I can feel a jerky hesitation that makes my head bop.

I decide that it isn't running right, and I wait for a car to pass to make a u-turn. During that Idle drops as far as about 500rpm, and I have to blip the throttle at standstills to not stall. I get it home, engine RPM at about 400rpm before she stalls in the parking lot.

So far I've:

• tried cleaning the intake parts, and I've sprayed everything out there with carb cleaner to check for leaks.
  • I have had ICV out and can confirm the valve opens and closes when I shake it, ICV busses with the key on start position.
  • I've tried unplugging the ICV while the engine is running, RPMs are unaffected. Taking the ICV out the boot stalls the engine.
  • I've tried unplugging the TPS, and the idle start jumping between 800-1500rpm like I've read many people experience if their ICV is broken.
  • I've tried unplugging the AFM while the car is running and the car instantly stalls
• I've checked the FPR, and there's no fuel in the vacuum lines. My FPR has a funky T joint at the end of it with one line going to the plenum and one line going to one of the coolant hoses that runs to the throttle body in what seems to be a valve.
• Sprayed carb cleaner everywhere, idle never changes
• blown a cigarette into the intake thru the PCV-tube while holding the throttle open. No leaky smoke - but I'm building a smoke tester I'll test with soon.
• Verified spark on all six cylinders. Spark plug on cyl 6 has the extra connector which is plugged in.

I've been bugging the great people on the r/E30 discord about this, and Noseko found this video for me:

https://www.youtube.com/watch?v=dFI1YNPSoLA

My ICV flaps, but it definately doesn't spring back like that. Could the issue have been this all along? Mine is the 3-pin L-shaped ICV

[e30vert]

Well you need 3 things for proper combustion. Spark, Fuel , and Compression.

Borrow a Fuel Pressure Gauge setup from the local autoparts place. Disconnect the fuel hose where it meets the Fuel Rail. Near the bottom of the Intake Manifold Runners on the Passenger side. Plumb the Pressure Gauge inline using the T fitting that is provided in most kits. Start the vehicle and monitor pressure. Report back with pressure reading here.

You could also do a dry compression test on each cylinder as well and record thier measurements.

[It's Soda Not Pop]

My wiring to my fuel pump has been acting up lately. My car will start and hesitate. But it I wiggle the connector to the pump it quits and runs great. So it could be a wiring gremlin as well. Is there any codes when you do the stomp test? How old are your relays?

[oelholm]

Well you need 3 things for proper combustion. Spark, Fuel , and Compression.

Borrow a Fuel Pressure Gauge setup from the local autoparts place. Disconnect the fuel hose where it meets the Fuel Rail. Near the bottom of the Intake Manifold Runners on the Passenger side. Plumb the Pressure Gauge inline using the T fitting that is provided in most kits. Start the vehicle and monitor pressure. Report back with pressure reading here.

You could also do a dry compression test on each cylinder as well and record thier measurements.

I doubt is fuel as it lights up alright to begin with - nonetheless it's a good shout and I'll buy a biltema Fuel Pressure Gauge and see if I can find a T-fitting that fits! I changed my extire fuel system from pump thru filter up to the engine with new lines. I hope nothing has gone wrong!

I did a dry comp test a while back. I don't remember the numbers off my head but they weren't great - that being said I doubt it's that that made it run great and then poorly one day to the other.

My wiring to my fuel pump has been acting up lately. My car will start and hesitate. But it I wiggle the connector to the pump it quits and runs great. So it could be a wiring gremlin as well. Is there any codes when you do the stomp test? How old are your relays?

No clue about my relays. I changed fuel pump last year. I'll have a look as I have the bench out anyway!

Thanks both!

[e30vert]

[QUOTE=oelholm;n10095411]

I doubt is fuel as it lights up alright to begin with - nonetheless it's a good shout and I'll buy a biltema Fuel Pressure Gauge and see if I can find a T-fitting that fits! I changed my extire fuel system from pump thru filter up to the engine with new lines. I hope nothing has gone wrong!

I did a dry comp test a while back. I don't remember the numbers off my head but they weren't great - that being said I doubt it's that that made it run great and then poorly one day to the other.


If you are in the states Harbor Freight has a very reasonably priced option https://www.harborfreight.com/fuel-p...AaAlKyEALw_wcB

Relays is another good idea to pull and light sand terminals, dielectric grease and reinstall.

You can check the resistance of the 3 Wire ICV . Should read 20 Ohms +/- 5 Ohms from center pin to outer pins and 40 Ohms +/- 5 Ohms across the terminals.

[oelholm]

If you are in the states Harbor Freight has a very reasonably priced option https://www.harborfreight.com/fuel-p...AaAlKyEALw_wcB

Relays is another good idea to pull and light sand terminals, dielectric grease and reinstall.

You can check the resistance of the 3 Wire ICV . Should read 20 Ohms +/- 5 Ohms from center pin to outer pins and 40 Ohms +/- 5 Ohms across the terminals.

Im unfortunately not near a Harbor Freight - ive heard great things about their torque wrenches - i do live close to a biltema. If you're ever in scandinavia, give them a visit. Great car stuff for great prices and awesome customer service

They have a fuel pressure reader - and found a T-piece for a windscreen sprayer and two connecters, so ill have a try soon enough!

Ill have a look at the ICV pins - i checked them a while back, and I think they had too high resistence but im not sure. I checked the solonoid today while the car was powered, and it springs back just like the video - so atleast that isn't the issue!

[oelholm]

Alright, time for a little update.

I've done the smoke test and found a small vacuum leak by the L from the ICV to the intake as well as a leaky valve cover. I've sealed everything up, and car idles perfectly at 800rpm

It however still takes nearly a minute to crank, and power is still at around 20%. I'm going to readjust the valves and change spark plugs, but I doubt that will help. I'm worried it's a fuel issue, but my pressure reader doesn't plug into the 8mm fuel hose of an E30. I need to find a t-piece that allows this.

[oelholm]

I lost my password, but now I am BACK.

Here's what I did, incase anyone googles and finds my symptomps:

I took the return hose off the FPR and pointed it into a jerry can as adviced by the bentley manual. When you short the fuel pump it should fill the jerry can with X amount of fuel - only nothing came out.

About a year ago I revamped the entire fuel system and I dropped in a cheap fuel pump and assembly from China. Lesson learned. I swapped out the pump for a Walbro unit but kept the housing, and oh boy does she run now! Before I reinstalled I could hear fuel slushing back into the tank by way of the return pipe. A big big overkill for fuel pump on our cars, but considering it's half the price of a Bosch unit I went with the Walbro. I recommend it!

[oelholm]

I lost my password, but now I am BACK.

Here's what I did, incase anyone googles and finds my symptomps:

I took the return hose off the FPR and pointed it into a jerry can as adviced by the bentley manual. When you short the fuel pump it should fill the jerry can with X amount of fuel - only nothing came out.

About a year ago I revamped the entire fuel system and I dropped in a cheap fuel pump and assembly from China. Lesson learned. I swapped out the pump for a Walbro unit but kept the housing, and oh boy does she run now! Before I reinstalled I could hear fuel slushing back into the tank by way of the return pipe. A big big overkill for fuel pump on our cars, but considering it's half the price of a Bosch unit I went with the Walbro. I recommend it!

Sidenote: In the mean time I got a new daily - a 320CI M54 E46 - and the exact same thing happened to it :p

[rmdashrf]

you put a Chinese fuel pump in the E46 too?!?! lol.

Glad you get it fixed and congrats on the new daily.

[oelholm]

you put a Chinese fuel pump in the E46 too?!?! lol.

Glad you get it fixed and congrats on the new daily.

Nope, original pump, but previous owner had the car for the last many years and never changed it, so I figured she was due a new one anyway hehe. Atleast oem e46 pumps with assembly and all is cheap still - wish ours were!

[oelholm]

you put a Chinese fuel pump in the E46 too?!?! lol.

Glad you get it fixed and congrats on the new daily.

Oh and thanks a lot:)

[It's Soda Not Pop]

nice glad you got it fixed