Tell me Im on the right track - Weird ignition problem - 91 3.3
I have a 1991 Aeromate yes that is right an aeriomate made by Utilimaster from 1986 to 1994. It has the old 3.3 as the powerplant and the yucky A604 trans 
Recently it lost most power and could barely pull. Discovered that it was only firing on one coil ( two cylinders ) ....... Easy fix, thought it was the crank sensor- replaced, thought it could be cam sensor replaced. Thought it could be the coil - replaced. Then thought it might be the pcm.
I have a 1992 which I can interchange the PCM and the 1992 will run fine with either pcm but the same result on the 91 as well as a few other 3.3 pcms from pull apart- only 1 coil is firing . Engine ran well before this so I was hesitant to think it was the timing chain and my gut now tells me it has to be a flexplate issue
. My snap on states I have both cam and crank signal and it will run on two cylinders. When checking the coil only one wire is sending a pulse signal - the other two are dead I have even tested the wires coming from the PCM to eliminate two bad wires . So... before pulling the trans this weekend - flexplate or timing chain more likely ? Truck has 150K but these vehicles due to their GVW sometimes over the limit makes me think more the flexplate. Thoughts ?
Thanks !
David
Recently it lost most power and could barely pull. Discovered that it was only firing on one coil ( two cylinders ) ....... Easy fix, thought it was the crank sensor- replaced, thought it could be cam sensor replaced. Thought it could be the coil - replaced. Then thought it might be the pcm.I have a 1992 which I can interchange the PCM and the 1992 will run fine with either pcm but the same result on the 91 as well as a few other 3.3 pcms from pull apart- only 1 coil is firing . Engine ran well before this so I was hesitant to think it was the timing chain and my gut now tells me it has to be a flexplate issue
. My snap on states I have both cam and crank signal and it will run on two cylinders. When checking the coil only one wire is sending a pulse signal - the other two are dead I have even tested the wires coming from the PCM to eliminate two bad wires . So... before pulling the trans this weekend - flexplate or timing chain more likely ? Truck has 150K but these vehicles due to their GVW sometimes over the limit makes me think more the flexplate. Thoughts ?
Thanks !
David
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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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17,276 Posts
Welcome to Allpar. I have worked on Aeromates in the shop. A local Dodge dealer sold them and I went to look at them and picked up a sales brochure. Great utility vehicle for an all-weather mobile standing-up shop in the back with a work bench.
The engine wiring harness was problematic on the ones that I serviced. The EFI system, coil pack and PCM are Chrysler components but the wire colors may not jibe with a Chrysler minivan service manual. Still, diagnosis would follow the same steps and component pin-outs would be the same.
I would start with getting an older (1991) minivan service manual and possibly the 1991 3.3L/3.8L Powertrain Diagnostic Procedures handbook. This will save you frustration, time and money. It will become your favorite tool besides your multimeter and test light. It may pay for itself in this repair alone.
I have doubts that the flexplate or timing chain is the problem and you might want to re-visit the coil-to-PCM wiring. It is one 'power in' wire (DG/Or?) and 3 out to the PCM for switching to ground to fire the plugs.
Those 3 may pass though an intermediate connector on their way to the PCM. Check connectors for damage, corrosion or push-outs.
A 'T' pin slid into the connector cavity next to the terminal is a better continuity test point than poking holes in wires.
Have you been able to get fault codes from the 'ck eng' light or scan tool? Any P0351 through P0353?
With the crank sensor out and a helper rotating the crankshaft bolt, watch the 'windows' passing under the hole for damage. By slightly 'rocking' the crank CW and CCW, do you see or hear any play in the flexplate?
Is it the same coil in the coil pack that is able to consistently fire every time?
Is your scan tool able to display cam/crank sync?
The engine wiring harness was problematic on the ones that I serviced. The EFI system, coil pack and PCM are Chrysler components but the wire colors may not jibe with a Chrysler minivan service manual. Still, diagnosis would follow the same steps and component pin-outs would be the same.
I would start with getting an older (1991) minivan service manual and possibly the 1991 3.3L/3.8L Powertrain Diagnostic Procedures handbook. This will save you frustration, time and money. It will become your favorite tool besides your multimeter and test light. It may pay for itself in this repair alone.
I have doubts that the flexplate or timing chain is the problem and you might want to re-visit the coil-to-PCM wiring. It is one 'power in' wire (DG/Or?) and 3 out to the PCM for switching to ground to fire the plugs.
Those 3 may pass though an intermediate connector on their way to the PCM. Check connectors for damage, corrosion or push-outs.
A 'T' pin slid into the connector cavity next to the terminal is a better continuity test point than poking holes in wires.
Have you been able to get fault codes from the 'ck eng' light or scan tool? Any P0351 through P0353?
With the crank sensor out and a helper rotating the crankshaft bolt, watch the 'windows' passing under the hole for damage. By slightly 'rocking' the crank CW and CCW, do you see or hear any play in the flexplate?
Is it the same coil in the coil pack that is able to consistently fire every time?
Is your scan tool able to display cam/crank sync?
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2 Posts
After I get the newer trans and new flex plate back in I will start tracing wires again. Is there any possibility the Trans controller could affect the firing ?The engine wiring harness was problematic on the ones that I serviced. The EFI system, coil pack and PCM are Chrysler components but the wire colors may not jibe with a Chrysler minivan service manual.
Same as chrysler on mine.
I would start with getting an older (1991) minivan service manual and possibly the 1991 3.3L/3.8L Powertrain Diagnostic Procedures handbook.
Yes I have a factory service manual but not the powertrain diagnositc which sounds like a good investment
I have doubts that the flexplate or timing chain is the problem and you might want to re-visit the coil-to-PCM wiring. It is one 'power in' wire (DG/Or?) and 3 out to the PCM for switching to ground to fire the plugs.
It is a 3 wire set up. I actually cut the two wires not firing and installed connectors. Neither was sending a pulse signal. This too I thought would eliminate the pass thru connectors. as it is coming right off the PCM. This is a 91 Aeromate which had the less desirable OBD1 which is pretty limited as compared to the newer ones. I bought a Snap on 2500 due to its OBD1 capabilities and it does appear the two are in sync from the trouble shooting module. Alas...... I had a factory remain A604 form my old Lebaron which went to the crusher in the sky with only 6000 miles on it so I decided to go ahead and R&R with the new one and the flexplate shows no signs of damage or cracks
Those 3 may pass though an intermediate connector on their way to the PCM. Check connectors for damage, corrosion or push-outs.
A 'T' pin slid into the connector cavity next to the terminal is a better continuity test point than poking holes in wires.
Have you been able to get fault codes from the 'ck eng' light or scan tool? Any P0351 through P0353?
Fault Codes on the OBD1 are two digit which isnt much better than a flashing light on the dash
Is your scan tool able to display cam/crank sync?
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
Joined
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17,276 Posts
I see that fault code 43 is for the coil primaries #1, #2 and/or #3.
Diagnosis is the same for all 3, there are just 3 different return wires to the PCM for each one.
Is this code 43 present when you extract them? Any other fault codes?
It should be a 4-wire plug into the coil pack. One DG/Or power in and Coil #1, #2 and #3 out to the PCM for sequential switching to ground. I don't think that the TCM would affect a partial coil operation issue.
Is it possible that some flexplate shutter windows got bent while maneuvering the torque converter up into position to be bolted in? I have seen this happen. (P.S.- I was able to straighten it).
Diagnosis is the same for all 3, there are just 3 different return wires to the PCM for each one.
Is this code 43 present when you extract them? Any other fault codes?
It should be a 4-wire plug into the coil pack. One DG/Or power in and Coil #1, #2 and #3 out to the PCM for sequential switching to ground. I don't think that the TCM would affect a partial coil operation issue.
Is it possible that some flexplate shutter windows got bent while maneuvering the torque converter up into position to be bolted in? I have seen this happen. (P.S.- I was able to straighten it).
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