Assist with M30b34 hesitation/surges during acceleration

[mini612]

I've been googling this problem that I have but have yet found a real answer, so here I am. I've completed an M30b34 motor swap into my E30. Everything went well, except when the motor is warm, the engine will hesitate during acceleration especially in 1, 2, and 3rd gear. Drives fine on the hwy. It does idle a bit high, 1k and sometimes 1200.

Some info:
- 059 ECU, NO performance chip
- G265 trans
- my E30 is, 85 Euro with 1 exterior fuel pump, no interior
- no over heating

These are brand-new parts:
- all gaskets are new
- new fuel pump
- rebuilt, all working properly 19lbs bosch injectors
- new fuel filter
- new vacuum lines
- new fuel lines
- re-man AFM
- re-man TPS
- re-man ICV
- new O2 sensor
- new spark plugs, rotors, wires etc....


The motor has been running bit rich and I was thinking I should switch the injectors back to the OEM, but I want to know what everyone is thinking prior to switching. Let me know your thoughts. Thanks

[JakeE30]

Could be something electrical, check your ground wires for your dme if it’s only happens in the first couple gears it could be because of the initial liftoff is causeing wires to touch an ground out maybe as for the high idle most likely a huge vacuum leak somewhere that you forgot to tighten

[george graves]

You've replaced a lot! Didn't see CPS. That's one of the key parts. FYI, I hear the cheap ebay units are garbage, and that OEM is key (but that's just second hand info - no first hand experience)

But that doesn't explain the high idle. Maybe two things are wrong at the same time? Maybe a vac leak as well? Stuck ICV?(hit it with some brake or carb cleaner)

[mini612]

Hey guys, thanks for replying, and yes the CPS are also replaced with OEM parts. As for electrical, I will have to check. Vacuum tubes are new and I have double checked and everything is where they should be.

Here’s more clue; I changed the FPR the other day to another that I have laying around and the car ran well with no symptoms until yesterday. When cold the car runs well, with no symptoms, but it’s when warm that it starts to stutter at low RPMs. There are no backfires.

The AFM appears to have no effects when I try to adjust it, coild that be the problem? Even though I’ve tried several afm, same symptoms. Could it be something that’s reading the signal from and to the afm? I’ve also tried switching ecu, and the car would run well right after I switch the ecu but then it will eventually start stuttering again at low rpms.

[Digital]

Just a random thought could it be the coolant temp sensor, I know normally on a cold start situation it adds more fuel.

[mini612]

The coolant temp is new therefore I don’t think it could be that unless it was bad from factory. The whole ignition system is new, including 8mm wires, new spark plugs, and new ignition coil. The afm does not correspond when I try adjusting the idle! The idle is still at 1k to 1200. The stuttering is usually at the beginning of gear 1, 2, and 3 and it usually happens when the car is warm. I have even tried several afm I have laying around and nothing! I will try another ecu I have laying around but I have tried this already a few months ago, still have the stuttering. Let me know if you guys have any ideas. Thanks

[george graves]

How bad is the hesitation? Like a zero spot of power until you hit 1200 - 1500 rpms?

[mini612]

How bad is the hesitation? Like a zero spot of power until you hit 1200 - 1500 rpms?

The stuttering/hesitation gets pretty bad; Feels like spark plugs are not sparking, occurrs when accerating hard; while normal driving, it feels like a short hiccup and back to normal. I am thinking it’s fuel related. Doesn’t make sense because I have all new fuel lines, new fuel filter and new fuel pump.

Again, the car idles a little high but it idles fine and smooth. The RPM does t correspond to me adjusting the afm. The AFM is currently set at factory setting, but no matter which way I turn it, the rpm remains the same.

[tschultz]

Battery to chassis ground??

[Bearmw]

Maybe consider taping a fuel pressure gauge to the windshield and going for a drive ?

[TobyB]

The stuttering/hesitation gets pretty bad; Feels like spark plugs are not sparking, occurrs when accerating hard; while normal driving, it feels like a short hiccup and back to normal.

Back in the old days, bad or overly high resistance spark plug wires could do that- it's harder
to light a full cylinder than a partially filled one. So you'd get hesitation under heavy throttle,
lower revs.

Just one thing that's happened to me.

t

[mini612]

Back in the old days, bad or overly high resistance spark plug wires could do that- it's harder
to light a full cylinder than a partially filled one. So you'd get hesitation under heavy throttle,
lower revs.

Just one thing that's happened to me.

t

That’s interesting. I am using 8mm BAV wires, they were brandnew when I installed them. I also installed new rotor, new spark plugs, new performance coil, and new cap. The car runs very smooth at idle even though it idles at 1k to 1200. It starts stuttering when I sudden accelerate in gears 1, 2, and 3, and at lowering rpm. It drives fine on the hwy and at higher speed.

I can double check the grounds again but I checked it a few times and everything looks good.

There appears to be good fuel getting into the engine so I am leaning more towards electrical issues.

[mini612]

How bad is the hesitation? Like a zero spot of power until you hit 1200 - 1500 rpms?

It is bad enough to feel no power, and it jerks the car, basically misfiring.... is what it feels like. I’ve done many m20 engines and played around with a few m30 but I haven’t run into something like this.

[george graves]

I'm racking my brain. The "19lbs bosch injectors" I assume the stock chip will adapt to that? Or no? Does for a m20 - not sure why it wouldn't for a m30.

I keep going back to air fuel or spark. Seems you've replaced all the spark parts(cap rotor). Air, unless you have a squirrel living in your air box that's out.

[mini612]

I'm racking my brain. The "19lbs bosch injectors" I assume the stock chip will adapt to that? Or no? Does for a m20 - not sure why it wouldn't for a m30.

I keep going back to air fuel or spark. Seems you've replaced all the spark parts(cap rotor). Air, unless you have a squirrel living in your air box that's out.

I totally agree with you. I’ve never had an issue with this type injectors before. I’m looking at electronics now. I’m going to check every sensor connector to see if they’re within spec. I did this right after the swap and they were all perfect, with in spec. I’ll have to recheck. Last thing I’ll do is switch harness or upgrade to a newer management system. I have lots of m30 parts so I’m not really throwing money around.