1989rs2.8

I replaced the fuel injectors and fuel filter in my 1988 2.8 Firebird this weekend. This made my car run much better than it ever has since I've owned it. Throttle response is much crisper and idle is significantly smoother.

On the way to work this morning, however, I noticed a problem. At WOT when merging onto the highway, the RPMs got to ~4500 and then the engine just seemed to totally lose all power very abruptly. I let off the throttle a little and suddenly the RPMs began to climb normally again. I was able to recreate this problem every time that I tried WOT.

I'm thinking it's either an issue with the new injectors (which would be weird since they seem perfect except at WOT) or possibly some vacuum issue caused by removing/reinstalling the intake in the process of installing the new injectors. Any ideas?

FireInMe17

Did you replace the 0-rings around the injectors? It doesn't really make sense that it idles fine if you don't have them in place but if your worried about a vacuum leak it would be work checking. Is the idle speed correct? If the idle is a little faster than it was before then you could very well have a leak somewhere.

1989rs2.8

Thanks for the reply. I bought remanufactured injectors that had new o-rings installed on them already. The idle speed does seem slightly higher than it was previous to installing the new injectors, but I just attributed that to the engine running better now.

project89

iTrader: (1)

back in the day i had a similar issue, car ra great all around except at wot once the rpms started to climb. i had no check engine light or codes stored.i had istalled an afr gauge and thats how i found my issue. turns out the motor was going dead lean under wot.

the issue was a bad maf sensor.

so it could be something to look into, just dont run out and buy one though as i belive they are around 80-100$'s and it be stupid to just throw that much money at it to see if thats the issue.

for now i would check voltage at the tps sensor, check the o2 sensor, and check for vacum leaks though if u had a leak bad enough tom ake it run crappy at wot the thing would idle really bad as well

1989rs2.8

Very interesting. I will definitely check those sensors tonight when I get home. I thought the MAF sensor was a possibility, but I thought it was too much of a coincidence for something like that to die exactly when I decided to replace the injectors. You may be on to something though. I think I actually have a spare MAF from my Camaro I could try on the 'Bird tonight.

1989rs2.8

I didn't find any problems with any of those sensors. I even swapped in a different MAF that I know is good, and the issue was not resolved. I think I blame it on faulty injector(s). I got a different set that I am going to put in this weekend. Hopefully this fixes the problem.

One thing I did notice while I was messing around with the two MAFs was that the issue didn't seem to occur (at least not as noticeably) with the MAF connector unplugged. Is this because the engine/computer goes into some sort of 'non-performance' mode with no MAF detected?

1989rs2.8

The other thing I forgot to mention is that while doing some research on this problem, I found out that the refurb injectors that I put in were actually 17lb injectors instead of the 15lbs that the 2.8 originally had. While I'm sure this isn't helping engine performance, I would have expected a 'rich' indication from the O2 sensor, not the problem I am currently experiencing.

TomP

Sounds like project89 was correct! If the problem disappears with the MAF disconnected, that means it's a bad MAF - or a problem in the wires that go to the MAF. You might have to run the code 34 chart; yes I know you're not getting a code 34- but the chart checks over every single MAF wire. Here's a diagnostic I typed up a while ago, all you need is a voltmeter to check the wires with: https://www.thirdgen.org/forums/post...870-post4.html

(And yes, with MAF unhooked, the computer goes into limp-home mode, and uses a default value for the incoming air flow.)

[edit] Oh almost forgot; you asked about 15lb vs 17lb, the computer can compensate for it; it just adjusts the time the injectors are open for. I have 3.1 injectors in my 2.8 and pass the NJ smog tests no problem (even the old dyno tests).

1989rs2.8

Just an update:

This weekend, I swapped in a new (reconditioned) set of injectors, and a new fuel pressure regulator since I already had the intake apart. This combination of parts fixed the problem completely. The 'bird is back.

Thanks for all replies!