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1989 olds 88 injector not firing or erratic 3.8

Tiny
DAVIDJ7479
  • MEMBER
  • 1989 OLDSMOBILE 88
  • 75,000 MILES
Originally my car would not start, replaced the ICM, it then started but ran rough, so I replaced the coil pack, wires and plugs. Still running rough, especially when accelerating around 40 mph.

Took it to a shop and they said that #5 injector was not firing, not sure why. So I replaced the injector. When it starts cold it works, within 5 minutes it stops. Now I don't think it it firing at all.

I saw on another post about checking for 12v and pulse. With key on I have 12 volts on one side of the connector, also when running. When I hook up a test light to the positive on the battery the pulse side glows, then cuts off. When running it will be off and then glow for about 4 seconds, then turn off, maybe 15 seconds later it will start to glow, then turn off.

I checked another cylinder and saw a rapid pulse like when a plug would fire.

Does this mean bad ECM? I wouldn't think a bad wire would do that.

Your thoughts?


Thanks
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Monday, September 9th, 2013 AT 3:36 PM

36 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
To be honest, I don't think a bad wire would do it either. However, I would check it to make sure. Does it ever pulse?
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Monday, September 9th, 2013 AT 3:40 PM
Tiny
DAVIDJ7479
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  • 25 POSTS
When I checked out for 6 minutes or so off And on it did not fire. I will let it cool off and try again leaving it on to see if it fires

How would I go about checking the wire.
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Monday, September 9th, 2013 AT 3:53 PM
Tiny
DAVIDJ7479
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Just checked again for pulse. Did pretty much the same, light would come on for about 2 seconds then go off, about 30 seconds later the light would come on for a second or two. One time it was like a quick pulse, but nothing after that.

If I take the probe off of the connector, every time that I touch the connector the light comes on bright for a second or two, sort of like it is discharging or something?
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Monday, September 9th, 2013 AT 4:32 PM
Tiny
JACOBANDNICKOLAS
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That is interesting. I wonder if the wire is bad. Can you check it for continuity?
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Monday, September 9th, 2013 AT 6:05 PM
Tiny
DAVIDJ7479
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. Thanks jacobandnickolas for the response.

I checked with continuity tester. There was a steady beep. Checked resistance and it was 31 ohms. Your thoughts?
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Tuesday, September 10th, 2013 AT 4:53 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
The resistance sounds high. Can you compare it to another wire to a different (working) injector?
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Tuesday, September 10th, 2013 AT 5:36 PM
Tiny
DAVIDJ7479
  • MEMBER
  • 25 POSTS
I can. Will be tomorrow. Will it tell me anything if I ran the car, used a light probe connected to the battery and poked the suspect wire at the ecm to see if I get the ground pulse? If it is a bad wire I should still get the pulse at the ecm?
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Tuesday, September 10th, 2013 AT 5:45 PM
Tiny
JACOBANDNICKOLAS
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That is a good idea. And yes, if the wire is bad, the light should pulse if you are getting the signal right from the ECM.
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Tuesday, September 10th, 2013 AT 5:48 PM
Tiny
DAVIDJ7479
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  • 25 POSTS
Ok, checked resistance on other wires, is was about.5 ohms. So I took some speaker wire, spliced the wire at the ECM and ran it to the injector, now I have a pulse. :)

But, it runs like crap, when accelerating around 45, real bad vibration.(Pretty much the same as before)

A couple of things that I noticed, the negative pulse wires have about 500k resistance between them, also to ground. Should they be open when the car is off? Also when I was checking continutiy between the suspect wire, it shows continuity to the other neg pulse wires?
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Wednesday, September 11th, 2013 AT 12:09 PM
Tiny
DAVIDJ7479
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  • 25 POSTS
Also, very erratic idle. Checked codes on computer, none, just 12.
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Wednesday, September 11th, 2013 AT 12:44 PM
Tiny
DAVIDJ7479
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  • 25 POSTS
I drove it At lunch time. It had bad idle. Shake bad on acceleration. When I got home, tried to start it. It will not run. With gas pedal pushed it eill run a little but rough, backfires then dies
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+1
Wednesday, September 11th, 2013 AT 3:35 PM
Tiny
DAVIDJ7479
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Ok, I disconnected the Mass Air Flow Sensor, and it will start and run, a little rough though. It drives better, no major jerking around 45 mph. So confused.
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Wednesday, September 11th, 2013 AT 4:52 PM
Tiny
JACOBANDNICKOLAS
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Did you clean the MAF sensor or replace it?
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Wednesday, September 11th, 2013 AT 6:44 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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If you have a pulse to all injectors, that is great. I thought the resistance in the suspected wire was high. Now, I need you to pull the plug out from the cylinder that had the injector problem and check to see if it is still good. If the injector was injecting fuel all the time, it may have fouled the plug.

Let me know what you find. And sorry this is taking so long. It requires many steps to locate the source of the problem sometimes. We'll keep trying.
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Wednesday, September 11th, 2013 AT 6:48 PM
Tiny
DAVIDJ7479
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I did not touch the MAF sensor, the closest I came to it was replacing the air filter.

I will change the plug and clean the MAF sensor with the appropriate cleaner.

It's ok it is taking a while, it's my daughter's car, she has my truck.
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Thursday, September 12th, 2013 AT 6:10 AM
Tiny
DAVIDJ7479
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I replaced the plug and cleaned the MAF sensor with MAF sensor cleaner. No change.

Engine sounded really bad, loud. Chased down a vacuum leak at the PCV valve. (I had the shop change it out when they were troubleshooting and found the injector not firing. I guess the hose has rotted, when I removed the PCV valve, which I could barely get to, part of the hose came off with it. I suppose this is where the vacuum leak was coming from.

Before I pulled the PCV valve, I just held it down, most of the leak went away, still ran bad.

Now, I can't see where the PCV hose goes to? Surely I don't have to pull the plenum/intake?
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Thursday, September 12th, 2013 AT 11:26 AM
Tiny
DAVIDJ7479
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Ok, replaced the pcv hose, found another leak at the canister, now it runs with the MAF sensor connected. :)

It's running much better. It idles a little rough in gear. When accelerating I get a vibration, especially above 40 mph, let off the gas, it stops vibrating.
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-1
Friday, September 13th, 2013 AT 4:06 PM
Tiny
JACOBANDNICKOLAS
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We need to get your truck back. Lol My son has mine right now which leaves me stuck at home.

Is the car running in an acceptable manner?
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Friday, September 13th, 2013 AT 6:02 PM
Tiny
DAVIDJ7479
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Well, I'd like to get it without the vibration on acceleration. :) Almost feels like cv joint. But, 2 weeks ago it did not vibrate when cold?
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Friday, September 13th, 2013 AT 6:41 PM
Tiny
JACOBANDNICKOLAS
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You mean it feels like something other than the engine causing the vibration?
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Friday, September 13th, 2013 AT 6:54 PM

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