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running like.......


Rbenh

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1989, drove to airport where is sat for three days, got in, started it and it runs really bad. it shutters and sputters, backfires (only a couple times), rpms ramp up and down.

changed out the ignition module and the coil block, the camp and crank sensors. i got vacuum and good ground to engine block. As i noted it ran fine to the airport, all it did was sit in the heat.  gas at 1/2 tank, oil change a couple weeks ago. The diagnosis screens tell me nothing is wrong, any suggestions?

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Welcome to the forum! Have you checked the fuel pressure? If not I would do that first.  Instructions are in the How-to guides here on ROJ for testing the fuel pump. You can borrow a fuel pressure tester at your local auto parts store if you don't have one.

 

Another thing you could check is the Mass Air Flow (MAF) sensor. If you unplug it and the car runs better that is a good indication that it is bad.

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i disconnected the MAF and the throttle position sensor with no change. there was a brief moment when it ran. Just after i changed the coil block and the control module it ran good for a few moments. i revved it up a couple times, then it went back to bad. Could be gas but i drove it 15 miles, seems like it would have pumped out the water unless it is really bad.

No leaks in the lines so no pressure loss from that. Gas filter?

there was 1 odd thing, with it not running the ECM data indicated it had 20 rpm. Not sure if really makes a difference.

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The guess the problem could be bad gas or a clogged filter. You really need to test the fuel pressure while the engine is running so you can rule out fuel delivery as the problem. Once you know that is good you can concentrate on the ignition system.

 

It is really odd that it ran good just after installing a different ICM & coil pack. The ECM reading of 20 RPM definitely indicates that something isn't right in the electrical department. Does the ECM data (ED11) read 20 RPM all the time? And does tachometer on the CRT also read 20 rpm?  If so you might have a bad ECM.

 

Normally I would say the RPM problem is caused by the ICM because the tach signal originates in the ICM and is sent to the ECM. If you are confident that the ICM is good (I've known brand new ones to be bad), and the connector is seated properly with no bent pins, then I think trying another ECM is the next logical step if the RPM is staying at 20 all the time.

 

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Ronnie has covered the bases pretty well. Disconnecting the MAF shouldn't include disconnecting the TPS, the ECM needs some form of reference to indicate increased throttle. I have seen floating data like the 20rpm indication with engine off before, it may also show in other areas, but should not do so while running. Eliminate possible fuel pressure problem first. 

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well, checked the crank sensor plug, the cam sensor plug, the TPS plug, and the Oxygen sensor plug. then it ran better but still RPMS display a spike to 6500. then a E042 error came up "electrical issue detected". disconnected and reconnected the alternator then it started running crappy again. bad alternator winding's?

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Since this seems to change or move around if you visit random items, it seems like something that is common to all the various items. Possible items: bad grounds; fender behind battery, on radiator header by battery, under ICM and top passengers side rear corner of the engine behind power steering pump. Bad battery connection, both hot and ground or possibly at the alternator. Alternator can be tested off the car. The indication of rpm spiking is peculiar. The ICM rpm signal connects to the ECM, but the display on the instrument panel comes from the BCM. Is the cover in place on the ALDL connector? How is the actual fuel pressure?

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I had a similar problem with my Reatta one time that almost left me stranded while I was a long way from home. The engine would start and try to run and then it would sputter and die. While it was running all the warning lights on the instrument panel would flash randomly on and off as if the car was possessed by the devil. 

 

Lucky for me it got to the point where the starter didn't want to turn the engine over like it should. That lead me to finding the problem.  It was a bad battery cable connection. Even though the bolt was tight the cable wasn't clamped tight enough to the battery to make good contact. When I pulled on the cable it made better contact with the battery so the engine could start and I made it the rest of the way home.  If you can grab the cable and move it up and down, even when the bolt feels tight, you could have the same problem. Here is what I did to fix it. Battery Cable Checks & Repair

 

This may not be your problem but it is certainly worth checking.

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checked the battery terminals, cleaned them up. Need to know more about the crank sensor and ICM. Might be a short somewhere, RPM still spiking.

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4 minutes ago, Rbenh said:

checked the battery terminals, cleaned them up. Need to know more about the crank sensor and ICM. Might be a short somewhere, RPM still spiking.

What in particular do you need to know. I'll try to help and I'm sure other members will too if they can.  Have you inspected the wiring that goes to the crank sensor.  That might be a good place for a rodent to do some chewing while the car was sitting in the parking garage.

 

The is a tutorial I wrote for testing the ICM and crank sensor as well as some other useful tutorials on the ignition HERE

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I was away for a few days, Back finding a solution. So i verified the wires between the ICM and cam and crank sensors. Cleaned all three cable connections. I have 10vdc on the ICM i have 14.1 for Ohms on the injectors. The magnet is good on the cam. The crank sensor gives me 9 VDC, then 8.8 VDC then 0vdc.  checked voltage on TPS.

Disconnecting a plug or injector wire makes it run a bit worse but not other wise no much change. traced back vacuum lines, till one (big) goes into the firewall on the driver side and a small one goes into the passenger side, i do have vacuum. Next plan to get some gas dry stuff the see if that helps.

the catalytic convertor gets red while trying to find the cause. 

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6 minutes ago, Rbenh said:

The crank sensor gives me 9 VDC, then 8.8 VDC then 0vdc. 

That sounds odd. Is this the test you were doing as described in my tutorial?


Test for power going to the CPS

  • Make sure the key is in the OFF position.
  • Pierce the second wire [N] from the left side of the ICM connector (White/Black stripe).
  • Set multimeter to 50 volt DC range.
  • Connect multimeter Red + lead to the wire (White/Black stripe) and the Black - lead to ground.
  • Turn the key to the Run position but DO NOT try to start.

You should read 10 volts DC.

Do you read at least 10 volts DC?

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yes, had the 10VDC. the 9, 8 and 0 where the reading from sensor feedback. plan check fuel and piston pressure tomorrow. also got some gas dryer stuff just incase.

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Catalytic converter gets red hot??? Very late ignition timing or lots of unburned fuel in the exhaust. What sort of readings do you get in diagnostics at warm idle in park? Almost all the readings will give some possibly useful information so a snapshot of what they are may give a clue.

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well the fuel pressure is good, going on a trip again so it shall wait for me to return.

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Red hot cat, I would try a different oxygen sensor. Often overlooked and should be replaced as a maintenance item anyhow...

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whats next? still runs bad, not as bad but still bad. backfires, misfires, RPMs jumping up, ...... BCM?

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