This may seem like a rather lengthy read but please bear with me. My wife owns a 94 Bonneville that she bought from her parents. Her parents had the same problems with the car but now after a few years the problem is worstened. I will try to explain everything and I ask for your opinions, trials and tribulations.

The car to me drives if it has a clogged catalytic converter ( best explanation). It bogs when you give it gas, at any speed, and stutters when taking off. Also it takes awhile to get up to cruising speed. If , when braking, I keep the idle at 1500 rpm and take off the stuttering is not present but all else is. The best way to get up to speed is by lightly applying gas pressure. Sometimes while getting up to speed, if you let off the gas you increase speed better.

Okay......now that you think you got it let me get on with the rest.

When her parents owned the vehicle, nearly everything under the hood was replaced including the ecu. The only thing that was never replaced by them was the fuel injectors, which I recently did myself with refurbished/cleaned injectors.

None of these things have done the trick. Another thing I need to add is that we recently took the vehicle for a diagniostics test by a dealership, and our backyard mechanic, whom is also a very good professional mechanic by day. What the dealers comprehensive test shown is that our car is perfect except the ecu. Our personal mechanic used a MAC TOOL diagnostic tester and his also pointed out the ecu.The code his tester showed are as follows....p 1406, p1670, and p1640. The 1406 is because the EGR is not responding properly to commands from the PCM. The 1670 Is the drver 4 and the 1640 error is for the quad driver module.
Our solution.....buy a new one. Her father paid $1200 for an ecu when he replaced it and that didn't repair the problem. We paid $130 3 weeks ago and this didn't solve the problem so we returned it. Yes, you heard correctly.......don't mess with a po'd scorpio woman with car problems.
Now with that all said, several people seem to think that it may be due to bad electrical. Also, the wife found another read that sounded identicle to what her problem is and they replaced the booster control solenoid and the problem cleared itself.

Let me know any suggestions or testimonies please. Thanks. Bummed out hubby of a Bonneville owner.

Is the bonneville Supercharged or Naturally Aspirated?

I'm not finding any of those codes in a chilton'* manual either. I've actually had the QDM 4 failure code reccently and figured out what they cover. If i remember right, the QDM 4 covers the A/C clutch Relay ( not positive, but definaly a relay in the A/C system,) along with the low and high speed fan operation. Do you know if the fans are coming on? And does your A/C work at all?

What I really need to know for sure is that you are POSITIVE that those are the correct codes, as I'm not finding any of them in my manual here. Unless they're only listed in a Factory Service Manual in which another member with a 94 FSM will have to provide you more information on.

Good Luck

It is NOT super charged

See above post....edited.

Opps I jumped the gun.

The AC went bad about a month ago, It quite letting the serpentine belt spin. We put in a used unit. It did this studder before and after.

This problem started as a small studder has has gotten worse over time.

Yes these are the correct codes, I had the mechanic write them down for me.

The QDM 4 code prolly has something to do with your A/C.....I wish I could help you narrow it down to the part of the A/C that QDM runs, but I just can't remember. The fans are also tied in with the A/C though. Do your cooling fans work when you turn on the the A/C in your car?


I'm gonna try looking up those codes one more way....and see what I can't dig up.

Hmmmm thats what my car was doing a week ago when they put that new motor in......ended up being the knock sensor.....wow what a difference now.....

Keelz... you have an interesting problem and there'* many ways to approach it.

You tried changing the ECM, so we can rule that out.

These cars are known to act a little wonky if a bad ground or poor connection is present. One suggestion would be to clean up your battery connections at both ends of the cables to ensure you have good grounding at the firewall and starter as well as battery posts.

The boost control doesn't apply to your car, however it is good research..shows how much you are trying. Everything under the hood being replaced... Was the Cat replaced? My understanding is that anything over about 1/3 of throttle and it stumbles and sputters. Although it the car is pushing those codes most likely something electrical in that series of codes is bad.

I might have my QDM labels wrong..but this is the basics The QDM modules monitor electrical status of solenoid or relay driven modules and set a code in the ECM if it sees a problem. The Boost information you found is an example of something bad causing the ECM to act really crazy.

1640 QDM1 has to do with the evap purge sol (charcoal canister at drivers fender) it should click on and off after the car is up to temp and running 2-3 minutes. You can feel this with your hand. 1640 can also be the TCC solenoid which is internal to the transmission and locks up over 38 mph to save fuel. Since you are not saying the transmission acts funny I'd rule that out. But it'* something to think about.

1670 I think is the QDM4 is the A/C relay and both hi and low fan speed relays. When you changed the A/C did you get the freon refilled and see it working?

It really comes down to something electrical either having low voltage or bad connection or not working properly.

Hang with us and we'll have you testing away soon. How are you with a multimeter?