Ok I am having a problem with my 1986 SE, 2.8 Auto. Car runs and drives perfectly with the exception of one annoying problem. I have had this problem for about 4 months and it is getting progressively worse every time I drive it. It started when I replaced O2 sensor. The new sensor made car run much better overall, more power and fixed code 13 though.

I will be on the highway, doing about 65, and the car will start to jerk and cut out. Sometimes once, sometimes it will have a fit, for about 30 seconds of jerking. Today, I was driving home, and it had the usual jerking and cutting out fit, but quickly got much worse. It started out like it always does. It then started jerking uncontrollably and then the car just "stayed cut-out" and was acting like it was on three cylinders and I could not keep it above 50 MPH. It seems that when as long as it is "cut out" it is in 3-cylinder mode.

I also noticed it when I first started the car this morning, it wasnt running right. I gave it gas, and the rpms slowly crept up, running on three cylinders. It acts exactly as it would do if you removed one of the TBI fuses in the fuse block while driving. I never knew such a small, ongoing problem could get a lot worse in one day. This does not act like an ignition problem at all. If it were ignition, when the car cut out, it would not be running at all. When my car cuts out, it is just a brief period of running on three cylinders. (Quite annoying when the car will barely go 50 MPH)

During this episode, computer shows NO CODES. Great.

Any help would be greatly appreciated, as this car is my only form of transportation.

EDIT
I thought this may help

Parts thrown at the car in the last 4 months:
New Cap and Rotor
New ICM
Pickup Coil
Throttle Position Sensor (Fixed code 21)
Manifold Absolute Pressure Sensor (Fixed code 33)
Intake Air Temperature Sensor (Just decided it was time to replace it)
Idle Air Control Valve (Fixed unstable idle)
Oxygen Sensor (Got rid of code 13)
EGR Solenoid (Got rid of Code 32 for good)

so all the parts helped somewhat. Could it be possible a part is bad?

[This message has been edited by mattman134 (edited 06-27-2010).]

Fuel starvation or plugged cat

More likely fuel starvation

So you have "thrown a lot of parts" at it. Have you checked your fuel pressure?

[This message has been edited by phonedawgz (edited 06-27-2010).]

Thing is, It runs great at full throttle and only cuts out at highway speeds and idle. When it cuts out, it feels like it is running on 3 cylinders.

So you're saying that indicates to you that the fuel pressure is correct? I don't know if this is a fuel pressure problem or not, but I do know a way to find out if it is. Or you can buy more parts - I'd suggest an ECM. Might be a wiring problem - how about a front harness and engine harness?

If buying the gauge is a problem maybe just buy a fuel pump and put it in. If that doesn't work then buy the gauge and troubleshoot it.

[This message has been edited by phonedawgz (edited 06-27-2010).]

I have checked fuel pressure with my gauge. It checks out fine. I am starting to think that the power wire from the TBI INJ fuse to one bank of injectors has an intermittent open. this would cause the exact same prblem. Also the ECM controlled ground to turn the injectors on could be shorting to ground, causing all injectors on one side to stay open? I also just noticed a crack in the wire at the C500 block by the battery. C500 E3, which goes to the coil. the wire insulation is cracked and the copper wire inside is corroded. Could this cause this intermittent problem?

Thanks
Matt

Well sure if you drop the line to three injectors, they stop injecting. Any idea why it would be that it drops off at those particular times?

So you just checked it the fuel pressure or had checked it before?

I checked it as soon as i got home

Maybe the harness is abraded through and is shorting out on the block

A bad speed sensor (pickup coil) can act just like that. Next time, watch your tach closely. Does it jump around madly? If so, it's something to do with the pickup signal.

Yes I know you replaced yours. Is the connector on tight? Were the pins on the ignition module clean?

Your distributors magnet could also be weak.

DG

------------------
You Dream it Up -- I'll Build it

Rethinking it - you know this could very well be a bad ECM. If you had access to one to try the swap, it would be worth the effort.

As for the ECM, a brand new one was put in when it did this a year ago. The tach does not jump around at all, just as it would when the engine cuts out (50-100 RPM) so I have mostly ruled out igniton.

When it cuts out, it runs on 3 cylinders, but doesn't totally quit running.

my first guess was a Ignition Control Module starting to fail - but - that is on your list of replaced parts
my next guess is the actual ignition coil
both of these items are heat sensitive, and, freeway speeds do build up alot of heat in these cars made for 55MPH speed limits

Ok. I will try to replace the ign coil. I was experimenting this morning. I think I may have figured it out. I pulled one of the TBI INJ fuses and it ran EXACTLY like it did yesterday morning; running on 3 cylinders. I will probably replace coil anyway for peace-of mind. I think that maybe one of the ORIGINAL TBI INJ fuses in the fuse block may have a hairling crack in it. I will replace those also. I will than check the C203 to see if the connectors are making good contact.

Thanks
Matt Howard

IF you can get it to fail, and stay running bad - try each fuse one at a time and see which bank is failing (assuming that) Check your upper engine harness to main engine harness at the plug. Check the wires by the ecm.

Wiggle around the wires and see if you can get the trouble to re-occur. Tap the fuse block while the engine is runnign and see if that makes it fail. It would be much better to find the trouble before it leaves than to do a swap and just hope that it doesn't come back.

I have finally figured out the problem. I tracked it down to the Fuel Injector circuit. I thought I would wiggle the TBI INJ 1 and 2 fuses while driving. Engine cut out. So i replaced the fuses as cheap insurance. The next day, I was driving and it started jerking and running on three cylinders again. I thought I would never get the problem fixed, so I stopped, went back to the motor and wiggled the flat 6-pin injector connector, and it cut out and quit. I restarted the motor, and every time I touched the connector, it would cut out.

I took apart the connector and cleaned it out with electronics cleaner and "reformed" the connector terminals in each half, to make a tight solid connection. I plugged it in and started the motor. NO MORE PROBLEMS!!! It seems now that my engine runs smoother and idles steadier now.

I personally know a person by the name of David Howell that owns a 1988 GT. His car does the exact same thing. Only on his, every time it happens it blows TBI INJ 2 fuse. So either his TBI power wire to the 1,3,5 injectors is shorting to ground somewhere, or his EGR solenoid is shorting out. I asked him if he has the dreaded code 32, and guess what? Code 32. Hmm???... 80% of all V6 fieros have code 32 anyway, so i dont know if that is his problem or not. Awful coincidental though.

Matt Howard

[This message has been edited by mattman134 (edited 06-29-2010).]

Very cool!

Your friend has either a wire shorting to ground, or an injector shorting out internally

If you look at the schematics for the power to the fuel injectors, the EGR Solenoid is powered by TBI INJ 2 fuse. Could also be the solenoid shorting out.

Matt