Help please, weird random non-firing injector issue...

[madsedan]

OK, trying to chase down the last gremlin on my s50 swap the shop cannot figure out whats going on with the injectors. The car runs great on the throttle, no missing or hesitation, strong, etc. BUT, when in neutral it'll idle for about 13 seconds and then rev blips to around 1,200 before cel 1221 and rough idle, sounds/feels like its got a big cam in it. Once you put it in gear and give it a WOT run it runs normal again and the CEL goes out until it idles again for 13-15 seconds.

Because Texas emissions has the car idle for a bit before doing the run and not going WOT it throws the code and stays in it throughout the test, its way lean on the test, N is high but C is normal. Car has all new 2 1/2" single exhaust with new Magnaflow cat.

They have replaced sensors, swapped ECU's and MAF's, and injectors with no change. So recently they pulled the fuel rail and injectors and tried starting the car to cycle the injectors, all fired nicely except for one, nothing coming out. They thought that was the culprit so they swapped the injector and repeated procedure only to have a different injector do it, again they swapped another one out only to have a different one do it, crazy.

They checked the fuel pressure and its good, any ideas, electrical maybe??
I searched but couldn't find a thread describing this issue of random non-functioning injectors.

[RobertK]

1222 is 99.9% of the time a vacuum leak. Running lean is also another indication of this.

Do a smoke test or the old fashion carb cleaner test.

[madsedan]

I'll get them to check for a leak again, they swear up and down that they have double and triple checked everything for a vac leak, the line to the ICV and the one under the intake manifold are the most common.

[MaksV]

for me it was the o2 sensor. throwing exactly the same code with a M50 swap. Make sure the wires are correct.

[madsedan]

To bring closure to this and for anyone with similar issues in the future, it was a combination of injectors and a vacuum leak.
The bolt that attaches to the underside of the intake manifold holding the dipstick had been over tightened at noe time and popped a hole in the manifold.
They went through 3 sets of injectors to put together 6 good ones and it runs like a champ.
Picked it up today and its great, already threw the bilstein sports on the rear and will do the fronts over the weekend with the H&R race springs and start killing tires.

[ian e30 318is]

Dude I am having a similar issue that you had! On some cold starts the car idles at a decent RPM but sounds like I have a cam in it (which i dont...i wish lol). Then when I rev it pretty hard up to 3 or 4k a few times the problem goes away and it idles well...what the hell? Any ideas? I just put in the rebuilt 21.5lb injectors from MaksV, changed my MAF to a 3.5", added a dry air filter, a new TRM chip in a red label 413 ECU, and there are NO vacuum leaks anywhere. Ive had it smoke tested a fixed all of them. But I did notice that the first injector plug was cracked off on the plastic but I pushed it down fairly hard onto the injector and it didn't fix the issue. Halp meee please! haha thanks.

Ian

[328ijunkie]

Is your chip for 21.5 injectors?

[ian e30 318is]

Is your chip for 21.5 injectors?

Yes it is! Bought it from TRM