1990 Reatta stumbles at high rpm

[Guest bkcamaro]

i got a check engine light 2 weeks ago and it was a code for a MAF sensor. So i replaced it and as soon as i did that it started idle surging when warm. no check engine light but from past cars its the IACV. I replaced that and fixed that problem now its stumbles at high rpms 

heres a video. Someone said it could be the fuel filter and i replaced that being cheap and easy and glad i did do to that last one who did it put it in backwards. No change i am going to test fuel pressure in the morning but any ideas. Also it only does it when under a load. It wont do it when in park or neutral.

[Machiner 55]

bk,

 

I'd say it is the Ignition control Module (ICM) located under the coil pack. If you car has the Magnavox coils, you should also check for the "green goo" that oozes out as they age.

Here's a link to Padgetts page regarding all things related to the coil pack and module. Once there, at the top right hand corner, click on "Articles and Fixes". Then, in the list on the left hand side of the page, click on "Replacing the Magnavox Ignition with a Delco Unit". There you will find all you need to know.

 

John F. 

Edited December 1, 2015 by Machiner 55 (see edit history)

[Dashmaster]

If it runs fine cold and starts after going into closed loop (warmed up) it could be OX sensor.  My 88 did that and the OX sensor was at fault. Ronnie's site has a tutorial to check the OX sensor.

[padgett]

To me that sounds like a secondary ignition problem (coils, plug wires, plugs) particularly is not setting a code.

 

If it were a fuel pressure issue can check by monitoring with a gauge or see if IPW (ED06) goes through the roof.

[Machiner 55]

It's the ICM.

Change it out with a known good one, new or from a salvage yard. 

Mark and remove the plug wires. There are three nuts underneath the bracket that holds the  ICM to the car. There is also a captive screw holding a wire connector to the bottom of the ICM I believe it requires a 7mm socket to fit the head of the screw. When reassembling make sure the contacts are clean and straight. No bent pins. There is an environmental seal (gasket) that goes over the pins. During reassembly, make sure you are using only one of these. Sometimes one will stay in the plug and the other will stay with the ICM. Pick the one that looks the best and pitch the other. A little dielectric grease on the pins before assembly wouldn't hurt.

Sometimes the mounting plate (Bracket) exhibits corrosion. Take a wire brush to it and apply a thin film of dielectric grease before mounting the ICM on the plate. Some people don't bother replacing the third retaining nut. (the one that was difficult to get to earlier) Won't hurt anything if you decide to use only the two. If you found green goo inside the coil-pack, that needs to be changed out. May be a good time to go with Padgett's Delco upgrade . Don't need to do this. If you have access to a good Magnavox unit, you can go with that.

 

Try it, then post another video just as you did with the first post. I can almost guarantee the shudder exhibited in you first will be gone.

 

John F.

[JeremyD]

My car is doing exactly the same thing at 3000rpm like clockwork. Makes it very difficult to accel onto the fwy or up a mild grade. I purchased a Delco coil pack from my local yard and apparently chose the wrong one. The mounts were completely different. Is some modification necessary or is it plug and play?

[Machiner 55]

Jeremy,

 

Here's a link to Padgett's page. Most everything you'll need to know about the ICM and coil packs. The link takes you to his home page . At the top right click the words "Articles and Fixes". Then click on "Replacing the Magnavox Ignition with a Delco Unit" found, third item up from bottom left hand list.

To answer you question, If my memory serves me (and it often times doesn't) it should be plug and play. If you are talking about the ICM mounting to the bracket which is bolted to the engine, that should not be an issue. there are only three bolts w/ nuts that hold the ICM to that bracket and they are in the same position regardless of whether it's the Mag. or the Delco being installed. Then you have six screws (two screws per coil set) that hold the three coil packs to the ICM. I don't recall there being a bracket change between the model years but that doesn't mean that there wasn't. Maybe someone else can/will chime in here to clarify.

But... if you are trying to install Delco coils on the Magnavox ICM... that ain't happen'n Cap'm.

Good Luck.

 

 

John F.

Edited December 16, 2015 by Machiner 55 (see edit history)

[padgett]

Plate was changed from a flat one to a more complex bracket in '94-'95. Think this is the one you need.

[padgett]

Can use the plate from a '91 only (left). The Magnavox ('88-'90) has the plate as part of the ICM and has fins (right).

Edited December 23, 2015 by padgett (see edit history)

[padgett]

Never hurtz to grab a few coils also. They are interchangable and can be individually replaced. The most common failure I see is one of the coils.

[DAVES89]

Already have extra coils. My buddy's think I could rebuild a car with what I have in inventory... 

[jonlabree]

My wife thinks I can build another car with all the parts I have.

Jon

[DAVES89]

Can use the plate from a '91 only (left). The Magnavox ('88-'90) has the plate as part of the ICM and has fins (right).

I went back and deleted my posts regarding the Delco upgrade as it was flawed. I didn't see it until Padgett posted this picture. Sometimes when I "do" something I am not "remembering" what I am doing and then later when I post what I did it is flawed information. So here is the correct info.

 There are at least two "adapter" plates that are are used on the Delco ICM/Coil Pack. The one we need is the one Padgett shows on the left. It has the three bolts that go through the plate that are needed to mount the ICM/Coil Pack to our engine bracket.

 The other "adapter plate" does not have the 3 bolts we need for our cars nor does it have a provision for the three bolts to be used in the plate. The ICM/Coil Pack will work you just have to get the correct adapter plate. The adapter plate that does not work with our car has 6 longer screws that go through the coils, then screw through the plate and into the engine bracket [but not our engine bracket].

 The adapter plate that we need once again has the 3 bolts that go through the adapter bracket and then through our engine bracket to mount the ICM/Coil Pack. The 6 screws that go through the coils and into the adapter bracket only are a bit shorter. The screws from the other plate are too long and will not work.

 When I was going through my ICM issues I already had a Delco unit on my car. I had the original Magnavox in my backstock and swapped it in. I then took the Delco unit that had been on my car and removed the "adapter" plate and put it on the 2006 Pontiac Grand Prix ICM/Coil Pack reusing the screws from the original Delco set up.

 So in conclusion one can use a Delco ICM/Coil Pack from almost any GM car using the 3800 engine from 1991 to 2008 but must have the adapter plate found on the 1991-1993 cars. The adapter plate I got yesterday came from a 1993 Buick LeSabre. The ICM/Coil Pack from a 2002 Buick LeSabre with 117,xxx miles.   

 I apoligize for any confusion.

Edited December 24, 2015 by DAVES89 (see edit history)

[padgett]

NP & why I take a lot of pictures. It is handy that I can just walk out to the back garage and find most anything (often several). Is much easier this century since I no longer need to scan in photographs (think my first digital camera was a Kodak DC-20 from the last millenium. two tenths of a megapixel. Not great.) Now my phone takes as good a picture as my Canon ELPH. Modern times.

 

BTW, the later mount is easy to spot. It is Not Flat.