Hey everyone, I've owned my 86 2.8 fiero gt for 3 years now and its has been a great fun car. This car has never seen winter, its all original even the exhaust. So this is my issue, Last summer I turned off my car and then when I went to start it, it ran terrible. I got it home and started to trouble shoot. I did a full tune up ( plugs, wires, cap, rotor, plugs, air filter). I tested the fuel pressure and it's 38psi. The pump runs for two seconds upon cycling the key, also replaced the egr valve since it had a small tear in it. I checked the exhaust for any restriction and its clear (unbolted the exhaust from the manifolds for a test). So that ruled out the basics. I did a compression test and I found that the compression was quite low on the front cylinder. I disassembled the top end and sent the heads out to be redone. It now has 150 psi x 6 cylinders. I have obd1 scanner that a local mechanic lent me ( doesn't use it anymore) and all the sensors are reading in normal values.
Now for the problem, The front head plugs are black, they seem to be loading up with fuel. The rear plugs are perfect ( nice light brown). I'm guessing that the injectors are getting the wrong signal and dumping fuel on the front head.
I would welcome any advice that would help me figure out this issue.My son gets his drivers license in 3 weeks and I want him to be able to drive it. He's so excited and I don't want to let him down.
Thx in advance, Medicman.
[This message has been edited by medicman (edited 03-30-2015).]
You may want to edit your Front/Rear references in your post....I think they may be crossed up.....
On a V6, the EGR control solenoid is powered by one of the injector fuses. Try unplugging it and check the wires. If it is grounding on something it may be affecting the injectors.
[This message has been edited by Gall757 (edited 03-30-2015).]
Thank you for mentioning about the front/rear confusion. I made the corrections. I tested all the fuses and they are all good, unless I'm missing some wierd fuses that are not located under the drivers side.
As for the EGR control solenoid, wouldnt it causes all the injectors to dump fuel if it was grounding? I will try unplugging it and see what it does, Nothing to loose. I'm at work tonight so it will have to be in the morning. If any more thought come up to try let me know, I have been scratching my head for way too long on this car.
So here is my short update, I checked the wiring from the EGR solenoid and I cant see any issues, I started the car and it blowing black out the tailpipes. I only ran the car for 20 seconds and shut it off. I touched the rear manifold ( clean burning plugs ) and it was cold, The front manifold was bloody HOT! Any clues?
fuel pressure maintains around 38 psi when the engine is shut off for hours, that kinda rules out leaking injectors. NEXT? ugh. I swear there will be a reward for who ever figures this out!!
Check the connector under the map sensor that connects the injector harness. Check for power to a ground key on, not running. Iirc, they always have power, the ecm controls them by grounding them. Your looking for pink for one bank and pink/white for the other. Check on one side of the harness, then on the other mate. You may have a bad weather pack connector pin. Fyi: The green/black and lt blue/black are the ground to ecm control wires.
Edited to correct wire colors after research
[This message has been edited by f85gtron (edited 04-01-2015).]
Thx for the info, I will check that later today, Since I'm colour blind, It would be nice to have a pic so I can make sure, I'm checking the correct wires. Makes the job a heck of a lot easier!
I just want to make sure I'm testing the correct wires. The 6 pin harness under the map sensor is the correct one I presume. Now when you advise to test power to ground, are you saying to put a test light from the positive post to the wires you indicated and look for my light to illuminate?
What does " Iirc " mean?
The green/black and lt blue/black are the ground to ecm control wires. Im guessing these wires are part of the 6 pin harness.
Since you say you have a scanner, hook it up again and check the readings, mainly the o2 sensor, if you are blowing black smoke the o2 should read rich, check your crosscount numbers. Check for any codes. Also try swaping plugs, front to back and see if the problem follows the plugs or stays with the cylinders.
Don't worry about asking too many questions, report back everything you try/test and the results.
So here is the update, I took some pics but have no idea how to upload them so I will do my best to describe what I have done.
1) I tested the wires below the map sensor and 4 out of the 6 wires have power, and have power on the other side of the connector. The only thing I don't know about this is that there are two pink white wires. One had power and the other did not.
2) I changed the plugs once this situation starting happening and there has been no change. Same 3 cylinder are getting black (cylinders 2,4,6) ugh!
3) I hook the scanner up again and when the car started, the cross count was 000 and showing lean. After about 30 seconds the cross count varied from 000-010 and is showing rich condition 02 volts are 0.47
So unless I did something wrong, I'm still hunting for the problem. I am really appreciate the help everyone is suggesting. My son is driving me nuts to get this car running nice again.
On a side note, when the car starts, the head (2,4,6) gets hot fast. Again I have undone the crossover manifold to check for a blockage, made no difference.
The heads have just been rebuilt. No ticking noises, great compression, 150psi on all cylinders. Were you thinking maybe burnt valves?
It has to be something that is isolating only that cylinder head. Anything like a EGR would effect all cylinders.
Early in the diagnose I unplugged the tcc and was looking for a change. So it do have code 33 showing. also have the map sensor code showing but that is when the car is put into gear, it wants to die after 5-10 seconds and triggers the map sensor code. I did try a different map sensor with no change. Again, a map sensor issue would affect all cylinders not just 2,4,6
[This message has been edited by medicman (edited 04-01-2015).]
The pink purple/white and tan wires are for the cold start injector. It's the 7th injector under the distributor, but only energizes during cranking in cold start situations. Try to switch the injector harness, front to back. If the opposite side fires and gets hot instead, then you have either an injector ground wire or ecm driver problem.
[This message has been edited by f85gtron (edited 04-06-2015).]
So If I understand correctly what you are saying, you want me to swap the injector plugins from the front head to the rear head? If so, wouldn't that cause a wrong impulse to the wrong cylinder?
Oh this is going to be fun! not exactly easy to get to. I will get that done today at some point. If it still does it on the cylinders 2,4,6 then that would indicate a head issue and not a electrical problem correct?
Yes, it's going to be fun. I suppose you could switch the grounds at the weather pack connector.....that would yield the same effect. Yes, if the problem is swapped to the other side, then you know it's the ground to ecm circuit, or ecm that's at fault. If it totally clears up, then the weather pack connector is at fault. If you haven't already, ohm out both sides of the weather pack and make sure all connectors are contacting first, before you go through the trouble of swapping this and that.
[This message has been edited by f85gtron (edited 04-03-2015).]
Yesterday became a nightmare with fixing everyones vehicles so mine had to take a back seat. I'm working all fri sat sun so I wont be able to get to trying the suggestions provided. I like the idea of swapping the ground wires, that will save me a ton of headaches.
I did test for power with the test light for power to ground at the 6 pin harness and 4 out of the 6 did have power with the key on the run position. I guess I could test for the ground wires for ohms.
As posted to me in a earlier post "The green/black and lt blue/black are the ground to ecm control wires", I do not have the same color of wires. Is it possible that on a 86 gt the ground ecm wires are a different color?
A pic or diagram would be very much appeciated if possible.
So a quick update, I tested the ohms on the grn/blk and blue/blk wires and there seems to be no issues there. I swapped the two wires around to see if the car would have the same affect on cylinders 1,3,5. I have just run the car for about 5 min. There was black smoke from the exhaust as per usual. I'm going to let it cool down and then pull the plugs. If I see 1,3,5 with black on them then its safe to assume there is a break in the grn/blk wire going to the ecm or the ecm it self is faulty. Is there anyway to test the ecm? before I go wire searching?
A noid light will cycle on off fast enough to test the injector pulses. But a better way is probably to pull one injector fuse, then replace and pull another. The 2.8 is so well balanced that sometimes, it's hard to tell when running on only three cylinders....just lack of power. If the motor dies when pulling one fuse, but not the other, then there's the suspect bank. I've got to read your post again to make sure I'm not spouting off redundant information. Sorry if i am. Ron
This image was shamelessly stolen from another thread in this forum...not far from yours. This should help with wire orientation.
Most colors are correct except for last one, which probably used to be tan, but now looks orange those last two are the cold start injector (7th) under the distributor.
[This message has been edited by f85gtron (edited 04-06-2015).]
Well I pulled the plugs on 1,3,5 and they are wet after doing the test of swapping the ecm ground wires (not sure if only running the car for 5 min was enough to make them black). I pulled injector fuse 1 and the engine died, I replaced it and started the car again and pulled the injector 2 fuse and it kept running with no change to the engine. So that being said, Injector one fuse runs what bank? and what is my next course of action? I really appreciate all the help. Son keeps reminding me that he is getting his license SOON!!! lol
I appears I have answered my own question. Injector one fuse is for bank 2,4,6 injectors. Those are the ones having issues with so where do I go with my search now. Thx.
Pull the fuse for the bank that killed the motor to verify. Then check for current at the injector connector to verify the dead circuit. Then ohm-out all the way back to the ecm to find if it's wiring or ecm. Check ecm grounds to motor, two 15mm bolts and terminal ends (under y-pipe attached to front, window side head). That's where the ecm grounds terminate. You've figured out the problem, now you just have to find it and correct it. Almost there!
Thx for the positive motivation! so help me understand, I will be checking the green-black wire back? What would cause the car to die when the fuse is pulled? Loss of ground?
Thx for the positive motivation! so help me understand, I will be checking the green-black wire back? What would cause the car to die when the fuse is pulled? Loss of ground?
The injectors fire because a pulsing ground is made in the ECM. If the ground is not made, or is not pulsing.....three injectors will not work (so there are 2 circuits for all 6 injectors). The wires that do this are the green and light blue wires, which go from the injectors to the fuse box, to the ECM. When you pull each fuse, it interrupts the pulses too. You need to confirm that there is a good circuit from the injector harness to the ECM. I don''t know which color is which injector bank, but you should figure that out as you pull fuses. If the car stops when you pull the fuse, that is the injector circuit that is working.
[This message has been edited by Gall757 (edited 04-07-2015).]
I wonder if a shorted injector on the troubled bank would cause this problem? Just thinking out loud. Seems to be a lot of dead bank and cylinder problems as of late. I hope it's not catching!
Ok that confused me a little. I was under the assumption that the injector fuse#1 which killed the car when I pulled the fuse was the bad bank. It would make sense because injector fuse #1 controls injectors 2,4,6. Those cylinders are giving me the black fouled plugs.
Injector fuse #2 does not kill the car when the fuse is pulled. (injectors 1,3,5)
Your saying that "If the car stops when you pull the fuse, that is the injector circuit that is working."
Unless I'm misreading something, it seems different to what f85gtron is saying
Either way, I'm going to pull injector fuse #1 and that should kill power to injectors 2,4,6, I believe that is the light green wire going into the 6 pin weather pack.
Got called into work so, I will test it out tomorrow and relay my findings.
Thx.Elliott
[This message has been edited by medicman (edited 04-07-2015).]
The inj fuse you pull and does nothing is the bad. The one you pull and kills the motor is the good one (that's the only one keeping the car going). I re-read my posts and they where misleading. Sorry.
Could you go back and check you have positive power to the injectors (pink and pink/white)? I think in one of your posts you mentioned one of the pink/white wires didn't produce voltage. My assumption is that the fouling bank is the one doing all the work and the dry one isn't getting fuel. If I've misunderstood, my advise is going to be crap.
My earlier question about the shorted injector affecting all on that bank might not have been worth asking because they're wired in parallel, not series.
Ok now that makes sense. I'm not sure if I have mentioned this but, Cylinders 1,3,5 exhaust manifold hardly heats up and cylinder 2,4,6 manifold gets hot fast. Humm that's a new turn of events. So maybe 1,3,5 injectors are the problem. Now it's coing together.
Like any messages, anyone can interpret them differently. I'm glad to know which wire to start checking.
I do have one last question, why would the plugs be so black on 2,4,6 if that is the good bank?
Originally posted by medicman: why would the plugs be so black on 2,4,6 if that is the good bank?
Computer controlled cars..... if the car is running on 3 cylinders, the O2 sensor could easily read it as a lean condition and tell the injectors to add fuel... I can't say for sure that this is happening, but stuff like this happens all the time....
Alright this is making more sense. When I have the scanner on, the car runs lean and then switches to a rich condition after 30 seconds. Now I'm starting to get excited that the end is in reach!
YAHOO!!! I found a broken wire in the harness near the firewall. I did check all the fuses in the past and they were all good but when I was about to put injector fuse back in, I noticed it was blown also. Anyways I hope this is the last of that issue. It revs out great and has the power you would expect from a stock 2.8.
it's running great except it idles nice and then loop idles. I know i did move the screw on the throttle body because it was revving very high (I know, stupid move) and I'm wondering if that is why its doing this. It was idling at around 2600.
Any thoughts on how to correct my stupidity to bring the screw back to factory settings?? Why the high Idle??