HELP 1991 SE IS NOW RUNNING ON 2 CYLINDERS

[ferrariguy]

I went out for a drive sunday in my 91 se and all at once it lost power. I pulled over and it sounded like it was on 2 cylinders. I pulled the number 4 plug wire off and it made no change same for number 1. it is firing on number 4 and number 1.I pulled the fuel rail off and swapped my number 1 inj with the number 2 and same thing. so I know it not a bad injector on 1-4. What controls the injectors on these cars ? is there a differant controler for 2-3 and 1-4 ? If so I would say thats the problem. any help plz. I have a service manual on engine management coming from dave bean for the se section missing in my service manual. I was hoping to make a car show this weekend with it. Thanks

[dr.hess]

I'd take a look at the coil pack. Are you getting spark on #1 and #4?

Edit: Yeah, I looked in my service notes. 1&4 are on the same coil pack. Thought so. Should be a GM part available at about any (US) auto parts store.

Dr.Hess


>> Edited by dr.hess on Tuesday 29th June 02:45

[ferrariguy]

Its not a firing problem. Like I said in my message. It is firing on 1 and 4. it acts like 1 and 4 injectors are not opening. this is a electronic injection system not the jettronic I dont know what controls the injectors. has to be a electric problem.thanks

[lotusguy]

Hi,

Check the obvious first, look for loose or disconnected vacuum lines as the ECU depends on proper vac signals more than you know. Pull the plugs and check their condition. Make sure you don't have a partially clogged fuel filter and also check that your timing belt didn't skip a tooth or two. Car will run, but like it's on two cylinders. Run freescan as well to insure it's not a compound problem. Happy Motoring! ...Jim'85TE

[igreenrover]

I had a VERY similar problem with my 89SE. In my case it was 2 & 3 that gave up. If I swapped the injector plugs over with 1 & 4 then I could get the car to run the same (just as poorly!) on 2 & 3, so there was no problem with the injector or spark side of the system.

As you have already found, 1,4 and 2,3 each run on their own circuits and that’s why you are having the problem. In my case it turned out to be the ECM that was not providing a signal for operating the 2,3 circuit.

Are you getting any error codes? I think you should be getting a 'current low' error.
It could just be the connection between the ECM and the injectors, or it could be the earth side of the injectors. I can find the wire colours for you to check if you need them?

www.pistonheads.com/gassing/topic.asp?f=17&h=8&t=60492

Drop me an e-mail if I can help.

Gareth

[sanj]

ferrariguy said:

Its not a firing problem. Like I said in my message. It is firing on 1 and 4. it acts like 1 and 4 injectors are not opening. this is a electronic injection system not the jettronic I dont know what controls the injectors. has to be a electric problem.thanks

If one of the pair of injectors fails it can drag the other one down with it. Measure the resistance of each injector with a digital ohmmeter set on the lowest scale, they will likely be in the neighborhood of 2 ohms or slightly less. Look for one that is lower in resistance than the other three, that will likely be the culprit. (Assuming it is an injector problem, anyway.)

Cheers,
Sanj

[Dr.Hess]

Injectors 1 and 4 are wired in parallel too. Check for continuity between the two injectors and J4D9 on the ECM. There is a harness connector (Pin A) and the plug on the ECM which could have a poor contact and cause 1&4 injectors to not work. According to the schematic, there is also a jumper between J4D4 and J4D8 in that circuit, so that is two more places for it to fail. If you are getting no pulse to ground at J4D9 and the jumper is intact, you may need a new ECM as the injector driver may have failed. GM part.

Dr.Hess

[ferrariguy]

I got a chance to check it out today. sanj u was right. It had a bad inj and when I unpluged number 4 number 1 started working. I took the fuel rail off and swapped number 4 with number 3. and now number 3 dont work and number 4 does. I think I will go ahead and buy 4 new injectors anyway. Thanks for all the help guys. Will let u know how it runs when I replace them.

[ferrariguy]

Well I replaced the injectiors and she runs smooth agian. Thanks for all the help guys.