Addicted To Boost Posted February 13, 2011 Author Report Share Posted February 13, 2011 Are 2.8 and 3.1 MPFI injectors interchangeable? Or are they higher flow on the 3.1s?? Quote Link to comment Share on other sites More sharing options...
mra32 Posted February 13, 2011 Report Share Posted February 13, 2011 if they are i might be able to send you two that nunzi sent me, I havent been able to take the plenum off, but i doubt that many could be bad and it still runs like it does EDIT: Maybe I should go do this now in the 2 hours of remaining daylight, think thats enough time? Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted February 16, 2011 Author Report Share Posted February 16, 2011 I replaced the 2 bad fuel injectors with a couple good ones from a 92 3.1 Cutlass. All injectors in the car now check out at 12.1 ohms. While I was in there, I replaced all the injector o-rings, upper intake gaskets, cleaned the throttle body, and new tb gasket and egr gasket. The result: During the day when it was in the low 40s, the car ran MUCH better- more power, ran smoother, no jerkiness, and it starts excellent now. I thought the problem was solved until I drove it tonight in the cold... its still doing the same thing, just not quite as bad now... Ideas? I haven't replaced the O2 or the coolant temperature sensor on it. There is no check engine light. Has new plugs and wires as of December, coils are all good, new ICM last week, all injectors check out at 12.1 ohms electrically and none are leaking. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted February 18, 2011 Report Share Posted February 18, 2011 Are 2.8 and 3.1 MPFI injectors interchangeable? Or are they higher flow on the 3.1s?? correct, both are 16.7 lb/hr also, for future refernce: the MAFs used for the 88 cars are similar to the low-frequency 85 TPI V8 MAFs, and were TOTAL failbus, more or less requiring the recall to fix a bunch of crap. the ECM only used the MAFs for fueling, using the MAP for spark control. Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted February 19, 2011 Author Report Share Posted February 19, 2011 After replacing the injectors, o-rings, upper intake gaskets, cleaning the tb, and tb gasket, I drove it around all day on Wednesday and it ran great... I was averaging 32 MPG with it... then on the way home, all of the sudden it started shuddering and shaking and I had to hold it at about 1/2 throttle to maintain highway speed... I limped it home 50 miles at ~15 MPG. I have no idea what is wrong with it now. It is running just like my TGP did when it lost a cylinder Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted February 19, 2011 Report Share Posted February 19, 2011 intermittent exhaust blockage? 2.8s sound better catless anyways. Quote Link to comment Share on other sites More sharing options...
BXX Posted February 19, 2011 Report Share Posted February 19, 2011 Replace the coolant temp sensor, they are cheap and cause sooooo many issues with the early MPFI cars. Best yet, check the wiring too, you may have an intermittent short. A scantool would be great to use to drive around and read the datastream to see what the CTS value is Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted February 19, 2011 Author Report Share Posted February 19, 2011 Replace the coolant temp sensor, they are cheap and cause sooooo many issues with the early MPFI cars. Best yet, check the wiring too, you may have an intermittent short. A scantool would be great to use to drive around and read the datastream to see what the CTS value is Which wiring should I be checking? Like I said, it ran perfectly for the majority of the day on Wednesday, and now it feels like it lost a cylinder or two... it runs just like the TGP did when it lost all compression on a cylinder... Ignition issue somewhere? It has a brand new ICM in it, the coils were good when I replaced the ICM, new spark plug wires, and plugs... All injectors were at 12.1 ohms when I put them in the car. Is it possible with the replacement of the two injectors (from a '92 3.1 MPFI Cutlass) would cause the others to go bad for some odd reason? When it warms up again and I have another day off, I'm just thinking of doing a compression test on all the cylinders... I hope this engine didn't suffer the same fate as the TGP engine. It sure is acting like it. Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted March 1, 2011 Author Report Share Posted March 1, 2011 Finally fixed it seems... I found I had no spark on the coil on the driver's side, so I replaced it (that coil was chinese aftermarket coil, the other two were GM units) with a jy GM unit for $4. I also took the ICM to oreillys and found it had failed already (brand new ICM that was on my car for not even 2 weeks!) and got a replacement ICM. With the new coil and ICM, it runs pretty well now... let's hope it stays that way! Quote Link to comment Share on other sites More sharing options...
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