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Horrible idle not drivable


johnemac

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Posted a week ago with problem thinking it was a bad cat, replaced cat to no effect. Car had ran great but while driving quit and would not start. Couple hours later it started up normally. Figured I would replace the crank position sensor. After replacement I got the bad idle. Cleaned the idle control and maf to no effect. Replaced idle control with spare, replaced icm with spare. Swapped coils one at a time. Took icm to be tested which it was good. Fuel pump pressure 42. Replaced plugs and wires. No codes. Starts right up but sounds like it is on only four cylinders. Tried to Ohm the coils but am getting nothing with my meter even replacing its batteries. This is an AC coil, I tried measuring a Magnavox and still could not get Ohms. Reading all he threads in search I came across one where the individual replaced the crank sensor and ended up with a bad idle but the thread ended with no results..............................90 convertible

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Well the O2 is a normal maint item so a new one will go in tomorrow. The ecm failed on an 89 I had and gave similar issues. It acts like wires are crossed but I went over the set up several times. There is a loud vacuum like noise by the vacuum reservoir but I check the tubing in the whole area around it and not finding anything. When you guys talk about an intake issue are you talking about a bad intake gasket or something else?

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If it runs bad in the first minute after starting cold, its not the O2 sensor, that only affects things when closted loop. TPS should show up on diagnostics screen (I forget which EDxx it is). I'd start by making sure the right coil terminal is going to the right plug.

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If it runs bad in the first minute after starting cold, its not the O2 sensor, that only affects things when closted loop. TPS should show up on diagnostics screen (I forget which EDxx it is). I'd start by making sure the right coil terminal is going to the right plug.

that is not always true. Twice after using seafoam (both times) I had O2 sensors go bad and each time it started cold and continued until the engine was warm.

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If it turns out being that grommet, be careful taking it out. I would get something with a small hook and pull outward, so you do not get anything left in the plenum. When I did mine a small piece of rubber was left behind, but does not seem to cause any problems. Even if that is not the problem, I would change it out anyway. I would pull the alternator to get better access to it.

Mike

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There is a loud vacuum like noise by the vacuum reservoir but I check the tubing in the whole area around it and not finding anything. When you guys talk about an intake issue are you talking about a bad intake gasket or something else?

You need to disconnect and cap vacuum hose going to the reservoir to see if that stops the noise or affects idle. If you have a vacuum booster, cap that hose and try it.

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Figured I would replace the crank position sensor. After replacement I got the bad idle. . Reading all he threads in search I came across one where the individual replaced the crank sensor and ended up with a bad idle but the thread ended with no results..............................90 convertible

If you have a spark tester or an inductive pick-up timing light, you can monitor each plug wire while idling to see if you have any with intermittent spark. If you do, revisit your damper for bent components or sensor for alignment issues.

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Well I went and got an O2 sensor and a PVC valve and a spark tester from Harbor Freight and the outcome is that I do not have spark from the topmost 6/3 coil. I swapped it with a junkyard spare to no avail. I should have swapped a known good one but I ran out of time. I won't be able to get back to it til Thurs but at least the issue is narrowed down.

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  • 2 weeks later...

Horrible just got worse (new mechanic). I was at my wits end so I took the car in to a new mechanic, I had moved and left my trustworthy mechanic. Anyway I call about the car (90) and the guy sez I do not have a 3.8 engine, probably a 3.3....not! and that the delco ignition should be the magnavox, and he knows as a fact that the intake manifold is incorrect for a 3.8. Ouch!!I might have to yank the car away Monday.

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I think if it were my car, I'd back it out of that garage real slow, keeping one hand on the steering wheel and the other on my wallet. Sounds like a real scary situation.

This is probably not your problem , but I would spray the harness that goes into the ICM with some contact cleaner and make sure the bolt is tight. I would also clean the plate the ICM rests on since it gets its ground through there.

Mike

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