E36 turbo stalling issue

[lisnowboarder]

Well I’ve dived deep into pages 3-4 of google search and still can’t figure this out so here I am. It’s a last glitch in an otherwise simple build. Car idle great, drives without issue, no cel, no surge, no hunting for idle, no lag in throttle response or hanging, no anything wrong with it. tell I push the clutch in for a red light or to coast and it will die 50% of the time. Immediately starts without issue and continues on. No boost leaks, icv is clean, maf is new, injectors are new, fuel pump and filter are new, no oil air filter.

I’ve bugged trm whom did the tune with a lot of other questions but before going back to them I was curious if anyone had any ideas other than tune related. I’ve got ~15 miles on this car an it sits because I can’t figure this out.

Gtx3582r, spacer and o ring engine.


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[vollosso]

Obd1 or obd2?


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[pbonsalb]

Under those conditions the throttle plate has just closed quickly. Maybe the issue has something to do with the tune or maybe there is a hardware issue like the adjustment of the throttle plate stop or the potentiometer.

[lisnowboarder]

Obd1 or obd2?


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Obd-2


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[daze450]

100% sure the ICV is good? I had cleaned mine thinking it would fix my issue.. Ended up taking the ICV out and it was still gunked up wouldnt move freely. Ordered a new one and fixed it for me. Similar issue to yours I spent a year blipping the throttle anytime i got to a stop sign or went to neutral for whatever reason.

[lisnowboarder]

100% sure the ICV is good? I had cleaned mine thinking it would fix my issue.. Ended up taking the ICV out and it was still gunked up wouldnt move freely. Ordered a new one and fixed it for me. Similar issue to yours I spent a year blipping the throttle anytime i got to a stop sign or went to neutral for whatever reason.

Well I’m pretty confident. Never had an issue on previous build and it wiggles and moves as expected. Also I have zero issue at actual idle. It’s only on the transition.


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[lisnowboarder]

Could it be an adaption issue? It’s a new ecu with the tune.


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[vollosso]

It’s 55% a maf issue


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[pbonsalb]

When you quickly close the throttle, air can back up into the HFM and disturb its reading. Where is your HFM located relative to the TB, any bends in the hot side pipe, and the BOV? Did anything of those things change or just a new tune?

[mitchlevy7]

Are you running a BOV and is it before or after the MAF? With a VTA BOV after the MAF, when it opens its letting out metered air, so the ecu gives the fuel for it, but the air isnt there so it will run rich enough to stall the motor. Do you have a wideband? If so, what is it saying when this happens?

[lisnowboarder]

Followed specs for everything. Maf is maybe 10” from throttle body. I moved it just far enough back that I had room for meth spray to not worry about hitting it and icv port. Bov is located on first bend after intercooler. They are separated by 17-20”.

It could be a bend issue. My maf is located right after a 30 degree bend. Or maybe my icv is opening an the proximity to my maf is making some turbulence.


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[pbonsalb]

My guess is that after about 10 years of tuning E36 turbos, TRM can get the idle right. The only exception might be is if they are trying some new HFM or injectors and have not fully sorted out the tune — in which case they should not be selling it yet. Defective hardware is possible, but pretty rare. I’d guess either the bend before the HFM or the location of the IACV port.

Hard to test unless you have a second set of hardware and a second set of hot side piping. Any chance you plugged your TPS into the IACV harness and vice versa? I think the connectors are the same, but think you would be experiencing more problems than just stalling on throttle closure if this was the issue.

[lisnowboarder]

My guess is that after about 10 years of tuning E36 turbos, TRM can get the idle right. The only exception might be is if they are trying some new HFM or injectors and have not fully sorted out the tune — in which case they should not be selling it yet. Defective hardware is possible, but pretty rare. I’d guess either the bend before the HFM or the location of the IACV port.

Hard to test unless you have a second set of hardware and a second set of hot side piping. Any chance you plugged your TPS into the IACV harness and vice versa? I think the connectors are the same, but think you would be experiencing more problems than just stalling on throttle closure if this was the issue.

I looked at that last night. The wiring harness makes that almost impossible with the lengths they have. Tough to diagnose this one without fabricating new pipe, flanges, etc. before then ill make a log of it dying and see what afr does.

[vollosso]

Post a picture of your charge pipes.


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[pbonsalb]

I looked at that last night. The wiring harness makes that almost impossible with the lengths they have. Tough to diagnose this one without fabricating new pipe, flanges, etc. before then ill make a log of it dying and see what afr does.

I think you got the wires right because the tps is the one with the boot and the iacv has the wires loose at the connector and I can see the boot next to the strutbar. Maybe you could test by easing the throttle closed more slowly or by borrowing a TB elbow with port and temporarily attaching the iacv to it while capping the port in the pipe.

[vollosso]

Somehow I missed the picture earlier.

I agree that the bend is very close to the maf which can cause problems.

I would pull the maf out and make sure it’s dry.



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[lisnowboarder]

Not sure if it’s a true test or not but on inpa I can see the throttle position sensor moving smoothly without jumping around.
Could I unplug the maf an rev to see if it idles after a drop?

Maf placement seems like the issue but I would think it would trigger an error code while driving for fuel trim.

Waiting for obd2 extension to run data logger


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[vollosso]

It’s unlikely trm retuned the maf failsafe tables. Unplugging it will likely not run.


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[lisnowboarder]

It’s unlikely trm retuned the maf failsafe tables. Unplugging it will likely not run.


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Bummer. So short of building a new new charge pipe I’m stuck troubleshooting.


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[lisnowboarder]

Well I might have fixed it pending a drive tomorrow. I was able to replicate the stall condition by reviving to 4500rpm at idle then let it drop. So I had something to work with.

I printed a new mounting flange, disconnected the intercooler an extended my maf harness so I could mount it in a new location for testing. My new location for testing was pre bov but I wasn’t driving anywhere. However when I started it I had a massive idle issue from bov being open at idle. Pinched the bov line to cure that an car does not stall with rpm drop. Relocated maf back to original location and doesn’t stall their either.

Upon googling the bov as the root cause it turns out my stall issue is in the instruction manual for setting bov spring tension by multiple manufactures. So tomorrow I’ll correctly set it stiffer. Tell then I’m hoping this is all done. No sure how this could be the cause. Doesn’t seem to make sense unless I’m somehow getting pressure buildup outside the throttle body when it closes an flow reverses back out the bov starving the engine.


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[pbonsalb]

Hopefully it is that simple. I had a BOV for years that was slightly open at idle with no issues (now using internal bypass valve on EFR turbo). Try tightening the BOV but obviously not so much that it does not open with the level of vacuum you get when suddenly closing the throttle — which is probably a couple of inches more than you get at idle. It may be that you will have to move the BOV further away from the HFM.

[milKt]

My MAF is even closer to my throttle body than that, with no issues.
TRM tune

8 years

[chikinhed]

My MAF is even closer to my throttle body than that, with no issues.
TRM tune

8 years

Not TRM tune but my maf is also closer to the tb, in between the bends and the icv air is taken from the silicon 90° tb boot (purchased from Technique Tuning). No idle issues.

One thing I’d like to add is that 15 miles of driving on a new obd2 build is probably not enough for adaptations to be fully adjusted yet and stalling when coming to a stop can be a problem until it’s adjusted. I had that same issue.

[lisnowboarder]

My MAF is even closer to my throttle body than that, with no issues.
TRM tune

8 years

Found a more likely issue. Bov seems to leak under vac. My assumption is used bov has a bad diaphragm.


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[pbonsalb]

Theoretically that should not matter — assuming the HFM is after the BOV. I was thinking more of a turbulence kind of issue near the HFM that is affecting the HFM reading.

Your issue could be something else — incorrectly adjusted throttle cable or stop. Generally when it ran fine before and I changed something and then it did not run fine, I study the work I did.