m20 stroker stumbles and quits (long, help)

[billybobjoseph]

Can you take off the cat and try to start it like that? It'll be really loud and piss off the neighbors but maybe it's plugged.

[NC325iC]

Alright,

The stroker was built by Pete McHenry, he gave me some limited info on it after it was purchased. It is bored and stroked to 2952cc with a late model m3 crank (i assume s50). Forged ultralight pistons, tool steel thin wall pins, low drag rings with oil ring support, "mildly" ported head (i head), schrick 284/272 dual pattern cam. All ignition components (except coil) are new stock replacements that i purchased from blunt. The coil tests out to be .8ohm primary and 5.38kohm secondary. fuel injectors are used 19# design 2 units in the stock fuel rail. FPR is a ireland engineering unit. ECU is a stock 173 with the WAR Chip, the engine harness is a slightly modified '89 i harness (modified per miller instruction to provide 12v to the MAF, and modified to be used in an 86 325e body). The intake manifold is stock i running gear, as is the throttle body. Throttle switch tested out fine in idle and part throttle with some inconsistency on the WOT switch. The exhaust manifolds are stock, into a stock cat which i purchased used from a junked car. o2 sensor is a wideband o2 from plx, output from the wideband to the ecu is a converted narrow band signal. I unhooked this output from the ecu when the problem first occured and the motor died quicker.

I just started it up and it idled for a couple minutes then gave up, didnt even get out of the blue this time so i dont know if its even temp related anymore (unfortunately i wasnt really eyeing it i was chatting with someone).

[nando]

it's actually closer to 30 seconds or less. the O2 sensor has a built in heater element, it doesn't rely on exhaust temperature for operation.

[Kershaw]

could be the o2 sensor. it only comes into play after it fully heats up, which may be a few minutes if its just idling.

[jlevie]

The thread title say stroker, but in the first post you say that the engine has:

stock i exhaust barring stromung muffler
stock i intake manifold and throttle
Miller PSIK and war chip with tune

I assume that you mean that it has:

I head, intake, throttle body, fuel rail, & injectors
I engine harness and DME
stock i exhaust barring stromung muffler
Miller MAF & WAR chip

The first thing I'd suggest is to revert to the I AFM and chip. That will pretty quickly tell if the problem is related to the Miller parts. If the symptoms are still present in that configuration I'd check the fusible link, replace the main & fuel relays with new parts and try a different DME. The symptoms don't sound to me like an problem with the exhaust so much as they sound like an engine management issue.

[nando]

nothing abnormal about the harness. for some reason, BMW put both wires on the gauge cluster coolant temp sensor, even though the sensor only has one wire and only one wire goes into the car. don't worry about the brown sensor anyway, it's only for the gauge. The blue sensor is the important one.

I'll have to double check my calibration of the ECU temp sensor, but that value doesn't set any alarm bells off in my mind. You should also check it at a colder temp if possible, and if you could at 90c. those might require removing the sensor, putting it in boiling water, freezing, etc.

[NC325iC]

just gonna list a few things im looking through here

with coolant at approx 75 or so degrees (ambient temp) blue sensor reads 1700 ohm btw 2 poles, brown sensor read 666ohm btw pole and grnd

Injector harness on engine side has only 6 pins (pin 3 is empty) while injector side has 7 pins

all relevant (not ac test) tests on bentley fuel system page 49 completed with good results

thats all i have for today, basically no new information

[NC325iC]

this will be on the list, but in my head it doesnt really make sense. If it were going to be an internal problem coming on by heat i would expect it to be pretty gradual, whereas the car runs fine and then all the sudden it just stumbles and dies. im starting to think its some electrical thing its just figuring out which it is. I am still gonna test the exhaust next. then i will likely replace the coolant temp sender and do alot of electrical tests.

[billybobjoseph]

PS, if you do try this be careful not to burn your fingers.

[billybobjoseph]

I had that problem too. If you do have to replace it make sure you get a Bosch one. When this happened to mine it didn't cause it to die however, otherwise I would assume one of the many things that can make a car run rough when hot. I think I would do what the above guys said and if nothing works, compression test it cold then compression test it when warmed up and hope to hell the readings for each cylinder are the same both ways.

[iX-treame]

Is it always after the vehicle warms up, and does it run just fine while the temp is in the blue?

^^^My coolant temp sensor was toast and made my AFR go wack so test that out.

[billybobjoseph]

Is it always after the vehicle warms up, and does it run just fine while the temp is in the blue?

[NC325iC]

ruled out relays, swapped them coupe-convertible and vice verse, convertible ran fine coupe still died the same way after it idled and revved just fine for a while.

I also ruled out that it was my electric fan sucking all the power away from the engine (when the fan kicks on the engine takes a little stumble but recovers normally) i unhooked it just to check.

Anyhow it still does the same thing, it runs perfectly for a few minutes (temp needle got out of the blue) and then kinda out of nowhere it just wheezes and dies.

will test exhaust next... any more suggestions?

[NC325iC]

Fired it up today with the hood up to keep an eye on the fpr. It fired right up and idled for about 5 min never a waiver in the fuel pres. No sooner than I close the hood and sit down to go for a spin than it starts to sputter, pop the hood quick to see the gauge and its rock steady. I'm gonna try the open exhaust this weekend, or I'll try to replicate the issue on my other e30 by plugging exhaust.

I did hear some faint rattling in the cat area, whether it was actually from the cat or not is unknown.

[billybobjoseph]

That is one sharp car N2MYE30