Stumped (Page 1/6)
Gizmo0816 JUL 10, 12:30 PM
I bought a 88 i4 notchback, about 6 months ago I think.
When I went to see it I was told it didn't run, so I replaced the spark plugs and it started right up first try in a couple of cranks and didn't exactly idle well, but under power it felt great.
Drove it home 3 hours, (I know not the smartest decision but I don't have a way to haul a car), interstate speeds, didn't give me a single issue.

It did throw code 42 and 45. I fixed 42 with a new fuel filter (pump was new so I knew it probably wasn't the pump), 45 with a MAP sensor I think. It now throws no codes cept 12 like it's supposed to. I also did try to start the car while the code reader was in it because the booklet said to do that to wipe the codes. Learned the hard way I was not supposed to, I don't know if it damaged the ecm or something but I haven't noticed any particular issues tied to my stupidity.

However, it has developed some new issues. It will never start on the first turn of the key, it'll just keep cranking, but it will start on the first crank on the 2nd turn of the key dependent of how long you cranked it on the 1st turn.

It has a much nicer idle then it had when I first got it, but still has a rough idle at roughly 1.5 on start, little below 1 when it's warmed up. Sputters, pops, and vibrates are pretty consistent however almost nonexistent when it hasn't been started long enough for the engine to cool down to enviroment temperatures. I believe I also hear an occasional misfire, but this is only when it's idling, if I give it gas I've never heard it stutter, pop, a backfire, and the engine no longer vibrates as much.

I've replaced the coil packs, icm, 02 sensor, MAP sensor, TPS (this was a pure hail mary), spark plugs, and spark plug wires.

At this point the only thing I can think of is a vacuum leak, but I have failed to locate one and it will be going to a mechanic Tuesday to find one. It has to have one.
I don't believe it's just a vacuum leak tho, that wouldn't make sense for the starting issue right? It has to be electrical. It didn't do it when I first bought it.

Forgot to mention another problem, if it has been started and shut down after awhile and you wait about 10 minutes to restart it the tachometer will shoot up to 1.5 then down to a .5, back to 1.5, back down to a .5. Then it will either die after doing this for sometime or resume idling like normal (I guess abnormal, but it's this cars normal atm.). If it does die then it will never run, until you manually idle the engine with the accelerator, then you can actually hear and see the exact moment it remembers how to idle.

I don't know if I accidently damaged the ecm or something, but I don't really know what else to check.
Gizmo0816 JUL 10, 12:33 PM
I also want to clarify all those problems except me having to manually idle it arrived prior to me trying to start it with the code reader in it.

Ever since I ran it with the reader in it, I have to manually idle it if I start it from about anywhere from 5 to 20 minutes depending on how warm it is. Like I said before after it cools down enough it'll start and idle like normal.
It seems to have something to do with temperature, but I don't know what would cause the engine to Rev from near 1.5 to a .5 and just keep doing it til it idles normally or stalls.

Or I screwed something up.


Oh I also, have only had it stall on me once, but this was before I even started working on it. Ever since I began changing parts out it has never stalled on me and sounds great when running.

[This message has been edited by Gizmo0816 (edited 07-10-2024).]

cartercarbaficionado JUL 10, 02:38 PM

quote
Originally posted by Gizmo0816:

I bought a 88 i4 notchback, about 6 months ago I think.
When I went to see it I was told it didn't run, so I replaced the spark plugs and it started right up first try in a couple of cranks and didn't exactly idle well, but under power it felt great.
Drove it home 3 hours, (I know not the smartest decision but I don't have a way to haul a car), interstate speeds, didn't give me a single issue.

It did throw code 42 and 45. I fixed 42 with a new fuel filter (pump was new so I knew it probably wasn't the pump), 45 with a MAP sensor I think. It now throws no codes cept 12 like it's supposed to. I also did try to start the car while the code reader was in it because the booklet said to do that to wipe the codes. Learned the hard way I was not supposed to, I don't know if it damaged the ecm or something but I haven't noticed any particular issues tied to my stupidity.

However, it has developed some new issues. It will never start on the first turn of the key, it'll just keep cranking, but it will start on the first crank on the 2nd turn of the key dependent of how long you cranked it on the 1st turn.

It has a much nicer idle then it had when I first got it, but still has a rough idle at roughly 1.5 on start, little below 1 when it's warmed up. Sputters, pops, and vibrates are pretty consistent however almost nonexistent when it hasn't been started long enough for the engine to cool down to enviroment temperatures. I believe I also hear an occasional misfire, but this is only when it's idling, if I give it gas I've never heard it stutter, pop, a backfire, and the engine no longer vibrates as much.

I've replaced the coil packs, icm, 02 sensor, MAP sensor, TPS (this was a pure hail mary), spark plugs, and spark plug wires.

At this point the only thing I can think of is a vacuum leak, but I have failed to locate one and it will be going to a mechanic Tuesday to find one. It has to have one.
I don't believe it's just a vacuum leak tho, that wouldn't make sense for the starting issue right? It has to be electrical. It didn't do it when I first bought it.

Forgot to mention another problem, if it has been started and shut down after awhile and you wait about 10 minutes to restart it the tachometer will shoot up to 1.5 then down to a .5, back to 1.5, back down to a .5. Then it will either die after doing this for sometime or resume idling like normal (I guess abnormal, but it's this cars normal atm.). If it does die then it will never run, until you manually idle the engine with the accelerator, then you can actually hear and see the exact moment it remembers how to idle.

I don't know if I accidently damaged the ecm or something, but I don't really know what else to check.


ecm is designed for what you did. check sensors and such or find out why the fuel injection is acting up.
on the starting issue my 88 v6 does something similar where it takes 3 or 4 seconds of cranking to kick over. I haven't figured out why yet either since I replaced a dead pickup in my distributor with a new one (equivalent to your icm/crank sensor). honestly I would pull the plugs out and clean them and only do one at a timeto avoid mixing them up.
Gizmo0816 JUL 10, 03:26 PM

quote
Originally posted by cartercarbaficionado:

ecm is designed for what you did. check sensors and such or find out why the fuel injection is acting up.
on the starting issue my 88 v6 does something similar where it takes 3 or 4 seconds of cranking to kick over. I haven't figured out why yet either since I replaced a dead pickup in my distributor with a new one (equivalent to your icm/crank sensor). honestly I would pull the plugs out and clean them and only do one at a timeto avoid mixing them up.



You just reminded me of the other thing I replaced that I couldn't remember. I already replaced the fuel injector. I figured If something was up with the fuel filter it'd be smart to replace the fuel injector. I'll clean up the plugs, they are a little orange from the fuel cleaner I ran through it. So maybe. Thanks.

[This message has been edited by Gizmo0816 (edited 07-10-2024).]

Gizmo0816 JUL 10, 03:27 PM

quote
Originally posted by cartercarbaficionado:

ecm is designed for what you did. check sensors and such or find out why the fuel injection is acting up.
on the starting issue my 88 v6 does something similar where it takes 3 or 4 seconds of cranking to kick over. I haven't figured out why yet either since I replaced a dead pickup in my distributor with a new one (equivalent to your icm/crank sensor). honestly I would pull the plugs out and clean them and only do one at a timeto avoid mixing them up.



Oh and also when I started the car with the reader in it was not happy, engine sounded like crap and stalled out. Is that normal?
theogre JUL 10, 04:03 PM
Please stop comparing 87+ Dukes to other engines. This is completely different engine that only shares very few parts w/ other Dukes & Nothing for V6.

DIS Dukes ECM & PIM/ICM when "cold" can take Longer to crank, up to ~ 10-15 sec, on first try but will start. Try turn the key 1-2 sec, stop, then try again often starts faster then 1 long crank.

If still have way long crank....

Does F-pump running when have long cranking?
Turn key on but don't start then should run ~ 2 sec.
If want/need to check fuel pressure,,, see https://www.fiero.nl/forum/Forum2/HTML/146121.html TBI Test Adaptor for Duke etc.
GM spec 9-13PSI but should see 13 unless has pump or plumbing problems.

One "rule" is same for all OBD1 systems is Will Not turn On Fuel Injection unless first see signal from the ICM is Running first.

ECM doesn't see this for several reasons... 3 common...
Any to All "Grounds" on engine block & frame are crap & need fixing/cleaning.
ICM is missing the shield & causing problems to a fire.
ECM is "Dead" but seems to work because crack solder joints etc "kill" just 1 section so can't see ICM, turn On the injection, etc but check light work normal or even ECM scanner can still work too.

see https://web.archive.org/web...~fierocave/gmdis.htm & wire service to start.
then maybe ECM heat page because that will cause many headache.

Fix/clean all grounds then coat silicon or permatex green label brake grease.
Can try tapping the ECM case by hand as can disturb crack joints might work but if does ECM is Dead. Save the PROM to use it w/ replacement ECM.

42 is a "problem" w/ ICM or wires/grounds to it or nothing wrong... Some time ECM give this "bogus" code w/ OE PROMs but can't get new PROM that GM updated the program to run the ECM. But again fix/clean all ground because that will do same.

45 is Not MAP. Is ECM see O2 "Pegged" & running Rich too long. This often Is Not the O2 but other problems like F'd F-return push F-pressure > 13PSI or Iffy MAT or ECT sensors.

Expect to spend several hours read the cave because most "books" & a lot more have wrong data for 87+ Dukes.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Gizmo0816 JUL 10, 04:41 PM

quote
Originally posted by cartercarbaficionado:

ecm is designed for what you did. check sensors and such or find out why the fuel injection is acting up.
on the starting issue my 88 v6 does something similar where it takes 3 or 4 seconds of cranking to kick over. I haven't figured out why yet either since I replaced a dead pickup in my distributor with a new one (equivalent to your icm/crank sensor). honestly I would pull the plugs out and clean them and only do one at a timeto avoid mixing them up.



Cleaned the spark plugs and it started in the first turn of the key in about 6 cranks or 7 cranks. Hasn't done that since I got it, so I guess that was one of the issues. Thanks. I'll see if it continues to do that. Still crappy idle tho, but probably a vacuum leak.
Gizmo0816 JUL 10, 06:08 PM

quote
Originally posted by theogre:

Please stop comparing 87+ Dukes to other engines. This is completely different engine that only shares very few parts w/ other Dukes & Nothing for V6.

DIS Dukes ECM & PIM/ICM when "cold" can take Longer to crank, up to ~ 10-15 sec, on first try but will start. Try turn the key 1-2 sec, stop, then try again often starts faster then 1 long crank.

If still have way long crank....

Does F-pump running when have long cranking?
Turn key on but don't start then should run ~ 2 sec.
If want/need to check fuel pressure,,, see https://www.fiero.nl/forum/Forum2/HTML/146121.html TBI Test Adaptor for Duke etc.
GM spec 9-13PSI but should see 13 unless has pump or plumbing problems.

One "rule" is same for all OBD1 systems is Will Not turn On Fuel Injection unless first see signal from the ICM is Running first.

ECM doesn't see this for several reasons... 3 common...
Any to All "Grounds" on engine block & frame are crap & need fixing/cleaning.
ICM is missing the shield & causing problems to a fire.
ECM is "Dead" but seems to work because crack solder joints etc "kill" just 1 section so can't see ICM, turn On the injection, etc but check light work normal or even ECM scanner can still work too.

see https://web.archive.org/web...~fierocave/gmdis.htm & wire service to start.
then maybe ECM heat page because that will cause many headache.

Fix/clean all grounds then coat silicon or permatex green label brake grease.
Can try tapping the ECM case by hand as can disturb crack joints might work but if does ECM is Dead. Save the PROM to use it w/ replacement ECM.

42 is a "problem" w/ ICM or wires/grounds to it or nothing wrong... Some time ECM give this "bogus" code w/ OE PROMs but can't get new PROM that GM updated the program to run the ECM. But again fix/clean all ground because that will do same.

45 is Not MAP. Is ECM see O2 "Pegged" & running Rich too long. This often Is Not the O2 but other problems like F'd F-return push F-pressure > 13PSI or Iffy MAT or ECT sensors.

Expect to spend several hours read the cave because most "books" & a lot more have wrong data for 87+ Dukes.




Oh I remembered what I did to clear 45, cylinder 4 was misfiring due to a bad wire. The internals were coming undone on the spark plug boot. 42 hasn't been thrown since I replaced the fuel filter, because my booklet said it could be a problem with the est, fuel pump, or something else. I decided to change the fuel filter since i knew it wasn't the fuel pump it was the cheapest to start with and wouldn't hurt to change anyway. I think you might be right with a bogus code being thrown, can I also ask where those grounds would be?

I wasn't aware that the starting was actually normal then, this car is 16 years older than me so I don't know a whole lot about it or any other vehicle from its time.

So I guess that isn't an issue because it does exactly what you said it does. I haven't cranked it that long on the first turn, but it does almost immediately start when I turned it the 2nd time 1 or 2 cranks on average.

I can't remember if the engine did fire or not I know it didn't sound right, but I think I'm gas lighting myself into believing that it ran with the reader in.
However I was wrong about one thing in my original post, I never had to manually idle it before I started it with the reader in it, that started after I tried to start the car with the reader in it. So one problem did start after that. Is this just coincidence or did something possibly happen?

[This message has been edited by Gizmo0816 (edited 07-10-2024).]

theogre JUL 10, 10:30 PM
If By "reader" means jump ALDL A & B... nothing should be damage.
ECM may try shutting off IAC port because think trying to set main idle stop. See cave idle stop.

ECM Scanner don't care but may keep Idle @ 1000RPM while connected because ECM is "running 2 threads" & isn't made for this. See cave, ECM section.

700 TBI can leak in several ways... Top 3... (See cave 700 TBI)
Vac leak @ bottom where mounted &/or side ports.
Vac/air leak when 2 TBI sections meet.
Fuel Leak @ the regulator. Look w/ air cleaner cover off w/ engine running.

If have any or all of those, buy a "rebuild" kit w/ all soft parts including the reg diaphragm.
cartercarbaficionado JUL 10, 11:25 PM

quote
Originally posted by Gizmo0816:


Cleaned the spark plugs and it started in the first turn of the key in about 6 cranks or 7 cranks. Hasn't done that since I got it, so I guess that was one of the issues. Thanks. I'll see if it continues to do that. Still crappy idle tho, but probably a vacuum leak.


I figured so. plugs ain't supposed to be orange and can foul up quickly but a good brake clean and if copper plugs are installed a little sandpaper can work wonders. for the vac leak spray at the throttle body around the linkage and where it meets the intake with brake or carb cleaner. do have a fire extinguisher or hose nearby just incase and try to not spray the cleaner with too much pressure