1989 Bonneville SSE engine problems

[mbarcher]

Awhile back I had problems with a code 42 . Changed coil packs and spark sensor , crank sensor, egr valve , sparkplugs and wires and things worked well for awhile.
Now I have a problem with the engine backfiring and bogging out for the first mile then it seems to clear up . Also it seems to eat up the gas as it acts up , smells like it is flooding and in less then 30 miles have used a 1/4 tank of gas !
Any ideas as to what might be causing this problem ?

[clm2112]

Back fires are usually timing issues, so I would start looking there first. Though, if there's enough fuel being dumped into the system to flood it out, then the back-fire can be the excess fuel lighting off in the hot exhaust manifolds, and not caused by spark timing.

Do you have a scan tool that will show you the engines parameters while it is running? If so, start looking at the values for injector pulse width and the BLM's.. see if the ECM is creating the rich mixture in response to some other problem.

[Alibi]

First, check for codes.

Second, how many miles? Typically, the timing chain on an LN3 should be changed out every 100-120k miles to ensure that it doesn't stretch too much. It would have to have a significant amount of miles on it before the timing was off enough to cause the problems that you are having (I'm thinking somewhere around 180k-200k miles).

If its not the timing chain, I'd say you may have a bad ECM.

[clm2112]

Just a quick thought.... When you replaced the ECM, did you move the calibrator prom from the old ECM to the new one?

<added later: Disregard - I confused this thread with a seperate one from a person who changed out their ECM...sorry. >

[Alibi]

I don't think he's replaced the ECM yet. I had an '89 Buick Park Avenue that did a very similar thing and it cleared up as soon as I replaced the ECM from another Vin C powered 3800.

I had these symptoms:

-burning VERY rich (black smoke out of the tail pipe)
-random codes, different every time I checked them via a paperclip... code 63 seemed to be the most consistent though
-randomly "bog down", IE run very rough or seem like it would idle down and want to die

A "new" ECM fixed all this. I got one from a local junkyard for $40 so they aren't horrible.

[mbarcher]

Yes I have changed out the ECM and put the old prom into the new (used)ECM .
The car has 172,000 kms on it , so that works out to around 105,000 miles
Seemed to work good for awhile then started up running rough and flooding out it seems . Figured it might be electric connections , but wiggled, unplugged, replugged etc and still nothing !

[Jrs3800]

Where are you located? Its possible for the New used ECM to not be so good..

Is the Code 42 still present, and are there any other codes associated with the 42?

[wjcollier07]

When you changed the coil packs, did you change the entire assy with the ICM?

[Alibi]

Where are you located? Its possible for the New used ECM to not be so good..

Is the Code 42 still present, and are there any other codes associated with the 42?

X2 on this. Re-check for codes to see if anything else has been tripped since the last time you checked.

A few simple things: How old are the plugs and wires? When was the last time the fuel filter was changed?

100k miles shouldn't be enough to stretch the chain to the point of causing severe issues but keep in mind that it will need a new timing chain in the near future one way or another, but thats for a different issue for now.

[mbarcher]

When you changed the coil packs, did you change the entire assy with the ICM?

Yes .. both coil packs and icm were changed also installed "NEW" sparkplugs and wires

[mbarcher]

Where are you located? Its possible for the New used ECM to not be so good..

Is the Code 42 still present, and are there any other codes associated with the 42?

I'm located just outside of Winnipeg Manitoba.
As for the possibility that the ecm could be not so good , thats possible.
The code 42 has been only code I have found so far ...

Could the mass airflow sensor be causing this?

[Jrs3800]

Yes the MAF could cause that but even then the majority of the time it will have a MAF code..

Disconnect the batter for a minute... Reconnect the battery and then do the code test without starting the car... Does the code 42 come back right away?

[mbarcher]

Ok seems the MAF sensor was part of the problem ... also the wiring to the MAF had a bad wire so rewired and everything runs good now .
Thanks for all the help and suggestions, very very much appreciated!
mbarcher.