Same old problem
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Same old problem
1989 with auto trans, 51000 miles, no mods, except no egr or air pump or cats
bought this car 4 years ago. My second 89.
I have been working on this problem from the first day I bought it
at idle it has a slight misfire. It has no pattern and I can't figure which cylinder or cylinders is causing the problem
i worked it as though it was vacuum leak, but I can find none. I used sprays, smoke and plugged off everything, but it's still there
i have replaced or adjusted everything that I can think off. I replaced head gaskets and heads redone because of number 7 blown.
When i I say this, I am serious, the only part I can think of that I have not replaced is the distributor itself and the brake master cylinder I have extra distributor just haven't changed it out yet
numerous time I thought I had it fixed, just to discover I had not
if you were to check all my postings, you would see what I have done to try to fix this problem
can anyone one help me?
bought this car 4 years ago. My second 89.
I have been working on this problem from the first day I bought it
at idle it has a slight misfire. It has no pattern and I can't figure which cylinder or cylinders is causing the problem
i worked it as though it was vacuum leak, but I can find none. I used sprays, smoke and plugged off everything, but it's still there
i have replaced or adjusted everything that I can think off. I replaced head gaskets and heads redone because of number 7 blown.
When i I say this, I am serious, the only part I can think of that I have not replaced is the distributor itself and the brake master cylinder I have extra distributor just haven't changed it out yet
numerous time I thought I had it fixed, just to discover I had not
if you were to check all my postings, you would see what I have done to try to fix this problem
can anyone one help me?
Last edited by mlm0; Nov 4, 2016 at 04:18 PM.
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
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Team Owner
Joined: Jul 2004
Posts: 28,331
Likes: 3,245
From: Hartford WI
IF the injectors are good, maybe we can start looking at spark? Your IAC holds at 29 so it doesn't look like an air leak. In the garage, do you have a blue flame? How are the wires? Have you checked them for leakage?
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
anyone know the best way to see if the voltage is correct and consistent at fuel pump at idle?
could a worn distributor shaft or gear cause this problem?
Team Owner
Joined: Jul 2004
Posts: 28,331
Likes: 3,245
From: Hartford WI
replaced plugs and wires two times. Checked in the dark garage, and thought I saw a spark jump, so I replaced them first time. No difference
anyone know the best way to see if the voltage is correct and consistent at fuel pump at idle?
could a worn distributor shaft or gear cause this problem?
anyone know the best way to see if the voltage is correct and consistent at fuel pump at idle?
could a worn distributor shaft or gear cause this problem?
I think my scanner tells you the fuel pump voltage. Not sure if it is accurate or not but you can hook up a DVOM to the pump at the back. It is pretty easy to remove. Thing is I would check pressure since it is the easiest. If the pressure is good, not sure I would go further. Check WOT and see.
I would check the shaft as it sits for play. If I had to remove it, I would take it out but mark it first for easy install. Make sure you don't bump the engine or you will have to time it all over again. Have a trusted couple of people check it out.
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Fair enough. What did you replace them with? Decent quality or some "backdoor special" at the local parts house?
I think my scanner tells you the fuel pump voltage. Not sure if it is accurate or not but you can hook up a DVOM to the pump at the back. It is pretty easy to remove. Thing is I would check pressure since it is the easiest. If the pressure is good, not sure I would go further. Check WOT and see.
I would check the shaft as it sits for play. If I had to remove it, I would take it out but mark it first for easy install. Make sure you don't bump the engine or you will have to time it all over again. Have a trusted couple of people check it out.
I think my scanner tells you the fuel pump voltage. Not sure if it is accurate or not but you can hook up a DVOM to the pump at the back. It is pretty easy to remove. Thing is I would check pressure since it is the easiest. If the pressure is good, not sure I would go further. Check WOT and see.
I would check the shaft as it sits for play. If I had to remove it, I would take it out but mark it first for easy install. Make sure you don't bump the engine or you will have to time it all over again. Have a trusted couple of people check it out.
i have checked vacuum and it shows about 18, but does bounce lower just barely, in time with misfire
Melting Slicks
Joined: Jan 2014
Posts: 2,176
Likes: 378
From: Lunenburg MA
One of the terminals on the ALDL connector is for measuring fuel pump voltage. Have you measured fuel pump pressure at idle? What chip is in the ECM? Is it stock? Try taking an inductive pickup timing light and putting it on the plug wires one at a time. Watch the flash for 30 seconds or so. See if it misses.
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
One of the terminals on the ALDL connector is for measuring fuel pump voltage. Have you measured fuel pump pressure at idle? What chip is in the ECM? Is it stock? Try taking an inductive pickup timing light and putting it on the plug wires one at a time. Watch the flash for 30 seconds or so. See if it misses.
stock chip
Pro
Joined: Jun 2009
Posts: 697
Likes: 30
From: Kansas City, Kansas
Have you done a "power balance" test to try narrowing it down to a specific cylinder? Your description of the inconsistent vacuum with the idle drop makes my brain say valvetrain instability, usually in the form of a valvespring failure.
Ignition is still a possibilty.......does the symptom get worse with humidity?
Ignition is still a possibilty.......does the symptom get worse with humidity?
Instructor
Joined: Oct 2016
Posts: 211
Likes: 20
From: Raleigh NC
Monitor the voltage with a digital vom. Duplicate the problem in the driveway and connect jumper cables from a running vehicle and see if the problem goes away. If compression is good I think whoever mentioned voltage is on to something. Luckily that's easily verified.
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Have you done a "power balance" test to try narrowing it down to a specific cylinder? Your description of the inconsistent vacuum with the idle drop makes my brain say valvetrain instability, usually in the form of a valvespring failure.
Ignition is still a possibilty.......does the symptom get worse with humidity?
Ignition is still a possibilty.......does the symptom get worse with humidity?
how do you do power balance test?