Greetings, I am trying to fix an engine miss and backfire in my 1990 deville
I have replaced thus far: cap/rotor/ ignition module/map senser/egr valve
plugs wires, ecu.
When i replaced ecu it ran good for couple hours, only to return to previous
problem.
Starts and idles fine, when driving on level road surface-seems ok- don't really
feel the miss too much. When flooring the accelerator it misses, and when it is under load-up a hill
severe missing/some backfiring.
Pulled 2 plugs today both very black-one wet -one dry
Only code it shows is vss vehicle speed senser.
My speedo hasn't worked in a year.
Problem started a month ago.
I had to a mechanic who checked fuel rail and fuel pressure was ok,
Another mechanic told me senser pickup in distributer,usually works or doesn't,so I
didn't replace that.
Help- I'm about ready to give up
Thanks
Chris

 

Is this a pfi 4.5 Do you have factory service manual and/or know how to use on board to monitor data. Spark plugs were for which cylinders? If you disable AIR system by disconnecting hose to AIR management valve what happens? Scope test could be helpfull. If distributor is not correctly installed cam sync signal will be off, causing injectors to spray at wrong time.

 

Thank you for your response.
The motor is a 4.5. what is pfi??
No manual but i am buying one today. Good idea
I tried to use on board data.
E.6.1 8.8.8
E.5.9 17,16,15,18
E.5.8 00
E.5.7 8.8.8
E.5.6 10,00
E.5.5 99
E.5.4 01
E.5.3 50
E.5.2 00
E.5.1 00
Don't know what they mean?
Will service manual show full use of diagnostics?
Air management valve disconnect----I will have to check
Spark plugs from cyl 1 (wet)and 8(dry), I think- Transverse mounted v8 which is #1. front right or rear right.?
I don't know what a scope test is? Timing light?
Distributor hasn't been pulled during my ownership. Maybe i should get one from junkyard.
Maybe this car would make a good boat anchor.
Does this condition sound like injector problem? i'm not good on injectors?
Does injector cleaner really do anything or is it a waste of $$ ?
Thanks again
Chris

 

No, you dont know how to use on board. #1 front head closest to passenger side. Sounds like you may have #1 & #8 plug wires crossed. Yes, Factory book will explain how to work on car and how to use On Board Diagnostics to correct problems.

 

Continuing to have missing problem.
Would the VSS vehicle speed sensor cause this problem?
This is the only trouble code that I keep getting

Also what does the electric motor that runs after you turn the car off do?
It's to the right of the air cleaner next to the wheel well.

Vent gas tank??

This one seems to run alot with key not in the ignition.
Thanks for your input
Chris

 

after a TECH response, we have no feedback or even an acknowledgment ..

[sm=feedback.gif]

 

E24 vss will not cause misfire. Pump on left fender well is for Electronic Level Control or rear air shocks...does not effect how it runs. I would suggest find someone in your area who knows what their doing to help you correct it. He should have worked at a Caddy dealer before 1996. You could post where your at city and state only and a member may be able to help you with one.

 

Thank you for the info on VSS and levelers.
What is driving me crazy is that 2 ecu's didn't throw any other trouble codes for this problem.

I bought a haynes manuel and am going to start eliminating emission type sensors by testing them. Then maybe get a distributor at a junk yard.
I could just buy all new sensors and fuel injectors and a distributor but then I'd have spent more than the car is worth.

Thanks again
Chris - Muncy,Pa.
PS the demo derby is coming up in july