1990 beretta misfire

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1990 beretta misfire

Postby indygurl » Sat Aug 19, 2017 8:21 pm

It's been awhile since I've posted on here most of you guys know my 1990 Beretta Indy. She has been put away for over a year now due to a broken seat last year after Beretta Fest, we fixed the sea and then now we're having problems with it misfiring We have replaced the injectors which was the sole problem recently had 3 bad injectors I bought all new injectors and had replaced them, tore the engine apart and had one that was leaking to make thiga easier to explain here is my post on facebook.
Ok so replaced intake gaskets today and she's running better than she did Thursday (staying started/not stalling) but she still has a misfire. So any guesses on what to check now? Plugs (again), wires, no vacuum leaks, its not old gas as this was just put in a few weeks ago. Also just took it for a drive and found that it only misfires under low RPMs what could be the problem any advice is welcome thanks in advance

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Re: 1990 beretta misfire

Postby ifixalot » Sun Aug 20, 2017 9:54 am

With those bad injectors, maybe the valves have carbon on them. Its a pita but do a compression check.

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Re: 1990 beretta misfire

Postby GT_Indy » Wed Aug 23, 2017 10:08 pm

1) When you replaced the intake gaskets, did you replace the upper and lower or just the upper?
2)When you verified no vacuum leaks, did you use a smoke tester and did you check every inch of plastic hose even to the cruise control and to the firewall?
3) If you pull the vacuum line off the fuel pressure regulator is fuel coming out the vacuum side of the regulator?
4) Compression test?
5) Fuel Pressure test?
6) Do you have an OBD1 scanner? A monitor 2000 or a APU1 auto prom from moates.net with the proper Tuner Pro files to read the OBD1 live data?
7) O2 sensor, IAC, TPS, Temp Sensor, CPS, all connectors plugged in correctly?
8) The Spark wire pairs are correct? 1-4, 6-3, 2-5, I believe its left to right when standing in front of the car and facing the front bumper.
9) When was the last time the IAC or TPS were replaced?
10) Did you check the coils are working good and not weak?
11) How old are the spark wires and the coils? I've experienced old wires cause misfires in the past on these engines.
12) All the new injectors seal and verified they do not leak under pressure?
13) Replaced O2 sensor after injector issues?
14) IAC valve clean and works good?
15) The vacuum line to the MAP, did you switch it with the vacuum line to the HVAC stuff?

I have a 3.1 MPFI at the moment myself which has a minor misfire which isn't that bad but just enough to notice, I plan to replace all 3 coils, spark wires, and spark plugs to correct the issue. It also recently had an IAC fail which caused it to slowly run worse and worse until it was stalling, and my O2 eventually fowled up and that needed replaced as well. I don't know if that helps but that was my most resent experience.

Can you post video of the engine running and misfiring, idle, revving, driving?

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