Need some help from the fuel injection pro's out there, please. I am working on a stock 87 GT with recent tune with all GM parts. The car ran great for about a thousand miles. Then, one day went to start it and it ran very badly, like it was only running on some of the cylinders.
Found the problem (kind of) which was a blown fuse for the front bank of injectors (2,4,6). Replaced the fuse, car started and runs much better but still not like it used to. It has a rough idle, but runs closer to normal as RPM's increase.
After checking a lot of things here's what I found...... on the rear bank of injectors (1,3,5) when I pull of a spark plug wire one at a time (while running) the engine stumbles and shakes until the plug wire is plugged back on (just like it should). It is all the same for each (1,3,5) cylinders.
Now, when I do the same procedure of the front bank (2,4,6) it only makes a slight difference on how the motor runs when I unplug each spark plug one at a time. All three cylinders act the same when unplugged.
I've tried everything I can think of including searching PFF's for solutions with no luck
Question is, I am planning on swapping the ground signal wires from the ECM (Lt Blue & Lt Green on the plug) to the opposite banks to see if the problem switches banks also. That way I can determine if I have a wiring or ECM driver issue. (Wiring color chart below).
I'd like input from the pro's on this, and any other suggestions that might help. Thanks in advance for your help & suggestions!
A - Pink/White - Switched power - runs to the injectors with the Lt. Green wires B - Lt. Green - Injectors to ECM C - Lt. Blue - Injectors to ECM D - Pink - Switched Power to the injectors with the Lt. Blue wires E - Purple/White - Cold Start Injector F - Tan - Cold Start Injector
------------------ "Because in a split second, It's gone"
Ayrton Senna
[This message has been edited by Ponnari (edited 11-07-2014).]
Do not pull spark plug wires on a Fiero when the engine is running. You will eventually damage the ICM and possibly the ignition coil. a 60 degree V6 should run smoothly on 3 cylinders. If it does not, something is wrong with the 3 cylinders that are firing. I suspect junk in the injector...have you had them cleaned?
A non fully closing EGR valve is a common cause for a rough idle. Remove the valve, clean out the carbon deposits from the seat and pintle. Make sure the pintle is extending enough to fully close the EGR passage.
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Yes you can swap the injector wires and see if your 'trouble' follows.
-------- +1 on never pulling plug wires on a running engine with electronic ignition.
[This message has been edited by phonedawgz (edited 11-08-2014).]
Leaking EGR (not EGR tube) problems show up most at idle and low air flow conditions. If you have this problem at WOT or near WOT, then look elsewhere.
Your injectors are 27 years old and so is your fuel pump. Check fuel pressure at the rail and with a test light verify that all injectors are being energized. If that checks out it may be time to get the injectors cleaned and flow tested.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Thanks "Dennis LaGrua" that is good advice if I were having issues on both banks but that is not the case. Your post doesn't address my question. Plus this happened instantly, not over time (re-read my first post & others that responded).
It is almost impossible for all 3 injectors themselves on one bank to mechanically / electrically fail at the exact same time. It is more likely that it is an ECM driver, or some other type of an electrical issue.
There has been mention here on the form of the exact same problem, unfortunately after searching I could not find were anyone solved their problem on other posts. Therefore I am still troubleshooting, and hoping someone else has had this issue and found the problem.
Injectors do not fail evenly. If there is a bad connection or blockage in one of them, the symptoms will be as you have described. It would make no sense to clean and flow-test just one injector, however, so they are always done as a group, as Dennis has suggested.
I do have brand new sealed OEM injectors & presure regulator, ready to install if I have to go that route. Only place I have to work on the car is outside and it usually rains here when I get a day off so replacing injectors will probably have to wait for spring unless I can fabricate some type of tent over the back of the car to keep things dry.
[This message has been edited by Ponnari (edited 11-11-2014).]
It is almost impossible for all 3 injectors themselves on one bank to mechanically / electrically fail at the exact same time. It is more likely that it is an ECM driver, or some other type of an electrical issue. .
Then check the injector harness for that bank. I thought that my advise to test for a signal at each injector was worthwhile but I guess not!
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Hi 85 SE VIN 9, good idea. I looked around locally within a few miles but the problem is I am close to the city and they are so regulated (no working on cars, boats, etc. it's in the contract ) and they all have video surveillance, which sucks! lol Thought about trying it anyway......
[This message has been edited by Ponnari (edited 11-12-2014).]
Yeah, it also depends on the market. There are many more around here so the rates are lower. It's might be in the contract here too, but they even told me I could use the power from the light. It's working out very well. It's cold now, but the heat of the engine is enough to work a couple hours in comfort. You can get those tent things, but that might be more trouble legally than working in a unit. I really suspect it's just one wire you need that you could do in between the raindrops. Look under lack of power or no power mid range, or something like that. It was not that long ago. Check the wiring diagrams, then check the wires from the injector fuse and the ground. If it's like the other guy there will be one of those that has extra resistance or no continuity, is loose, or intermittent.
[This message has been edited by 85 SE VIN 9 (edited 11-12-2014).]
Thanks "85 SE VIN 9" , I agree about the wiring. If it will stay dry I'm going to try and brave the cold and do more testing. also, I'm going check more storage places and ask them off the record about working on cars
------------------ "Because in a split second, It's gone" Ayrton Senna
Did you ever reset the ECM after replacing the fuse? And after the reset, drive the car over 25mph for a little bit, then turn off the car and start it again. This resets the idle.
Sounds like you have a bad injector (electrically) on the 246 side. They are wired in series (per side), so if one goes, they all behave in the same manner.
------------------ 1986 SE Aero coupe.
3.4 DOHC swap is complete and running, now just have to finish the rest of the car...
IIRC (and I do not have my wiring diagrams with me) all 6 injectors fire at the same time. Each bank has it's own power through 2 fuses, but the grounds to the ECM drivers are wired to fire all 6 twice, not 3 and 3. You could still have an issue between the harness connector and the point where the grounds are spliced together.
The single blown fuse suggests a short between the fuse panel and the affected injector bank.