: rough running 94



CadillacTerry
03-02-07, 10:05 PM
My 94 Fleetwood isnt running right cold or when accelerating a lower speeds. When its cold it acts like a carberated car w/ the choke problem,like its loading up and tries to shut off until I let off the throttle or drive like my grandmother.

After it warms up it only does it when I accelerate hard from a stop or go to pass. If I drive it like a Cadillac It does ok but not great.

It has an exhaust leak at the head from a broken bolt in the manifold. my thoughts are this:
1: the leak is leaning out the oxygen sensor causing the computer to dump more fuel in?
-or
2:The traction control light is on and the dealer said the computer needed to be replaced. This may have nothing to do with this problem at all.
-or
3: It just needs a tune-up.

Any info is helpfull.

caddycruiser
03-03-07, 11:13 PM
I'd say it just needs a tune-up, or at least a once over. There are a LOT of little things that can affect how it runs, from the ignition system to the fuel system, nothing really huge, and for a '94 pretty typical.

On the other notes, the exhaust leak--depending on how big--could be exacerbating the running issues, but I really shouldn't have that much of driveability impact itself.

And as for the traction control light, it very well has, I believe, an issue with bad speed sensors on the rear axle, but I'd have to search for them. Not a hard issue, though, and not an expensive thing either--I have to do this too, sometime, as my traction and ABS lights come on from time to time.

96Fleetwood
03-04-07, 09:43 AM
The exhaust leak is a major component and if your car has never had plugs & wires done.. that would make it run better. Your optispark might be bad as well.. but that is a $$$ bill.

CadillacTerry
03-04-07, 02:24 PM
Ok, I drove the car again today and here is a better discription of what its doing. When I puled out of my driveway it started acting up, it will accelerate a little then go quiet but not shut off, it will then get up to a speed of about 25mph. When I give it some gas the engine will rev a little then go quiet but not cut off (this happens very quickly) and it idles fine. about 2/10 of a mile or so down the road it straightens up and starts driving fine. the trans was rebuilt about 1000mi ago and the coil was just replaced.

Hopfully this info will help some.

96Fleetwood
03-04-07, 05:58 PM
It is hard to diagnose a problem like that without physically being with the car. I still bet the exhaust leak is one of the big problems.

CadillacTerry
03-05-07, 08:21 AM
I keep driving it and it gets a little better each time. I'm going to replace the computer, and at some point I may pull the motor and do a tune-up with MSD stuff, then drill out the studs and replace the manifolds w/ a set of headders and do some other motor work.

Thanks for all your imput.

96Fleetwood
03-05-07, 08:25 AM
If you do change the engine computer (PCM), make sure you use one from a LT-1 Fleetwood or you will need to get it reprogrammed. The Fleetwood has some different programs than the Roadmaster, Caprice, & Impala.

carguy16
03-05-07, 07:26 PM
stay away from the Caddy dealer. Pull the codes from your PCM and post them on here, for all you know your traction control switch could be bad.

XXL-VETE
03-05-07, 10:21 PM
There is no reason to replace the PCM .. if the car starts and runs .. chances are 99.98% that the PCM is fine .. Plugs and Wires and the exhaust leak for sure and it sounds like you may have an EGR problem .. that is a very common stumble problem with the LT1 ..

Kenny

Hammondsix
03-06-07, 08:02 AM
Get a Factory service manual off ebay or somwhere else. It will really help you diagnose the problem.

http://cgi.ebay.com/ebaymotors/1994-Cadillac-RWD-Fleetwood-Factory-Service-Manual_W0QQcmdZViewItemQQcategoryZ34212QQihZ002QQi temZ120088178332QQrdZ1QQsspagenameZWD1V

CadillacTerry
03-06-07, 08:23 AM
I'll probably try the trac swich first, but I am going to take the engine pcm out and have it flashed at work to see if that will help any. as for the egr, I havent thought of that and i'll have to check it out.

BCs71
03-08-07, 01:51 PM
IN your shoes I would definitely fix the exhaust leak first and then replace the o2 sensors. This is likely the cause of all the driveability issues.

Fuel trims are screwed up and degrading other sensors now...

N0DIH
03-09-07, 01:27 AM
Ok, first. Exhaust leaks are NOT an issue when cold. O2 sensors are NOT online yet. So that rules the exhaust leak out.

I have NEVER seen a exhaust leak cause more than a very minor change in BLM's. I have yet to buy exhaust leaks as legitimate issues. Sorry! Someone prove me wrong on it....

Honestly your problem sounds like a EGR valve that is not seating properly. Like carbon deposits on the pintle so it won't seal. How to isolate? WOT it won't be an issue. BUT, and EGR problem will always be there and not get better at any engine temp.

Ok, so what now? O2 sensors. I am fighting one now on my truck that seems to fail when cold, but then comes up later once it warms up, or the PCM just plains faults it out and then ignores it.

What codes do you have? That is key. I would be willing to bet you have an O2 problem. Advice: Get AC Delco sensors. I have learned WHY this is an issue. GM specs that the O2 sensor shell is to be grounded to the O2 sensor "LOW" lead. My aftermarket sensors are NOT. I fought and fought with them till I figured that out. I manually grounded it and all is fine now.

So, save yourself the pain, spend the extra $$ and get AC Delco sensors. It is well worth it.

CadillacTerry
03-09-07, 08:41 AM
Ok, first. Exhaust leaks are NOT an issue when cold. O2 sensors are NOT online yet. So that rules the exhaust leak out.

I have NEVER seen a exhaust leak cause more than a very minor change in BLM's. I have yet to buy exhaust leaks as legitimate issues. Sorry! Someone prove me wrong on it....

Honestly your problem sounds like a EGR valve that is not seating properly. Like carbon deposits on the pintle so it won't seal. How to isolate? WOT it won't be an issue. BUT, and EGR problem will always be there and not get better at any engine temp.

Ok, so what now? O2 sensors. I am fighting one now on my truck that seems to fail when cold, but then comes up later once it warms up, or the PCM just plains faults it out and then ignores it.

What codes do you have? That is key. I would be willing to bet you have an O2 problem. Advice: Get AC Delco sensors. I have learned WHY this is an issue. GM specs that the O2 sensor shell is to be grounded to the O2 sensor "LOW" lead. My aftermarket sensors are NOT. I fought and fought with them till I figured that out. I manually grounded it and all is fine now.

So, save yourself the pain, spend the extra $$ and get AC Delco sensors. It is well worth it.

There are no codes, only the stumbling problem.

N0DIH
03-09-07, 06:29 PM
I would lean towards EGR if no codes. But stumble is characteristic of lean conditions.

Look for broken/cracked vacuum lines. Look for problems in the Opti vent. If it is plugged on the fresh air side it will cause a stumble due to the Opti being in a high vacuum (hard to arc a gap when there is no air to jump through!)

Look for stuck PCV, cracked power brake booster line, EGR deposits keeping pintle slightly open, Opti vent lines broken, damaged, plugged.