Buick Reatta runing rough

[2seater]

It is curious but I must admit I have lost track of what year Reatta we are dealing with🙄 All my limited experience has indicated the 8253 ECM is correct for the Reatta with LN3 engine. I have had a half dozen ECM’s, none had a red plug socket.

[padgett]

Sorry but missed before - that 1228786 has the square panel of a BCM.

[rben]

Strange, but that last shown ECM, is the one in my car. I see though that the Prom that i have is ANDM not the ANDP.  So

So checked the TPS and get a good read. Tucked the Oxygen sensor cable down to make sure it does not come anywhere near the rest of the wires.

Next thing, to get the exhaust taken care of. It has a leak near the converter so maybe that is causing some issue.es.

 

[padgett]

Yes, that is a Body Control Module. Can see the two prom sockets, one for the 27C256 program and the other for a 2816 EEProm that holds the changing ODO reading (and other mutable stuff).

 

In fact just found an -8786 in my spares. ANDM Prom.

 

 

 

 

[rben]

So i potentially have the right ECM with the right chips. Are these chips pre-programmed or do they need to be flashed with the data?  If they need a flash then i still have a possibility of it not being right.

 

[padgett]

Does it start ? If so what does ED99 read ? (Prom ID). BTW the ECM is against the passenger side of the car, about a foot right of the BCM.

[2seater]

42 minutes ago, rben said:

So i potentially have the right ECM with the right chips. Are these chips pre-programmed or do they need to be flashed with the data?  If they need a flash then i still have a possibility of it not being right.

 

Padgett knows more about this than I do, but if it is a stock replacement Prom (Memcal), and carries the proper identifier numerals, it has the correct program already loaded. It can be modified, but then technically, it should have a different part number. The Prom doesn't know any better and the programable part of the overall Memcal can be reprogrammed to suit different needs, like cooling fan operation, TCC lockup and others, but should also be relabeled as such.

[Ronnie]

On 7/30/2020 at 6:41 PM, rben said:

It is a bit of a shutter at the 50mph at 4th gear when you give it gas. If you give enough gas and it drops back to third it is fine.

As for the PROM i am not sure i have been trying everything else before taking on the the ECM. I don't have the tools or the equipment to download or verify the data on the ECM is right. This issue has to be data related somehow. As i mentioned it doesn't do the shutter thing with the MAF unplugged.  That tells me the ECM is running a preset program and not using the incoming data with the MAF unplugged. I thought is was the MAF but i have three of them and they all do the same thing.

 

The shutter may not be ECM or data related at all. When you unplug the MAF I think it prevents the ECM from going into closed loop. That will keep the torque converter from locking up resulting in less load on the engine when you try to accelerate. A shutter or stumble when trying to accelerate at low RPM with the converter locked up in high gear can be traced back to a weak ignition system a lot of times.  Don't get caught up in the high tech stuff and overlook the basics.

Edited August 4, 2020 by Ronnie (see edit history)

[rben]

EPROM ID 5784

[padgett]

Correct for an '89 Reatta

BCC

Size

Year

Release Date

Eprom

ECM

Prom ID

Scan ID

Platform

Engine

Disp.

Trans

Trans Type

Gear Ratio

ANNH

1989

32279

16125998

1228253

5999

5784

EB

LN3

3.8

AUTO

F79

 

[padgett]

Have you replaced the balancer ? What I am seeing would match a maladjusted CPS (Crank Position Sensor).

 

BTW much of what I don't see are diagnostic values (rpm, O2, knock, short and long term fuel... Are you having difficulties getting into or understanding diagnostics on the CRT ?

[rben]

I can get in to system, not clear on all the data bit i did notice the RPM was at 20 with the engine off. I am trying to find the cause of my rough running in overdrive, and low RPMs. After replacing plug wires, plugs, coil packs,  Ignition module, oxygen, cam,  and crank senors. Put in a new timing chain, gears, and adjustment magnet. I was working eliminating the ECM from the "cause" list. I checked the feed from TPS, tried 3 MAF units and still the same issue.

[padgett]

Still have to wonder if the CPS was installed correctly, would need to look at the waveform.

[2seater]

10 hours ago, padgett said:

Have you replaced the balancer ? What I am seeing would match a maladjusted CPS (Crank Position Sensor).

 

BTW much of what I don't see are diagnostic values (rpm, O2, knock, short and long term fuel... Are you having difficulties getting into or understanding diagnostics on the CRT ?

Asked the same question on July 7th?

[Ronnie]

18 hours ago, rben said:

I am trying to find the cause of my rough running in overdrive, and low RPMs.

 

Does it do the same thing in the driveway if you put it in gear, hold the brake, tightly, and then give it a lot of gas to put the engine under a load?

[padgett]

Might not do it then, my experience with secondary ignition problems is heavy load, low RPM, closed loop, LEAN condition like over an overpass in 4th lockup at 45-50 mph in cruise.. Really bad and could happen anytime but this does not sound like it.

[rben]

Checked all the plugs and cables, all where good. Took it for a test drive yesterday and it was great.Drove it today and it is doing the thing but not as bad and i now feel it in third gear as well. Watching the the data as it runs. I see the Oxygen sensor feedback, on then off at a "calm" rate of change. Then when it does the jerking/ miss-fire feel it blinks constantly. So either i have a sticking valve or the exhaust has a hole close to the sensor which could be part of the cause.

[padgett]

" blinks constantly. " not sure what you are looking at but think the blinking means transitions which you want. When not blinking it is either too rich or too lean and I forget which. What is the "short term fuel" doing ? Transitions are usually low at idle <6 and more at speed >10.

[Chrisssssssss]

Chiming in here, but here are my bad guesses...

 

1) I think it may be a bad connection somewhere. Maybe bad connection at the sensor, try wiggling all wires and connectors. Or I know it had been said before - bad ground. Try cleaning all grounds by disconnecting the grounds and cleaning with brake cleaner and sanding them clean. Make sure there is no cracked or brittle wires. Or even try adding a secondary ground wire and attach it to a bolt somewhere on the engine and running it to the (-) terminal on the battery. Somehow I really am flashing the loose or bad intermittant connection or ground somewhere.

 

1b) As a long shot too, could be a bad defective battery shorting out internally causing weird electrical interference/feedback - even same with alternator. Unlikely but possible. If you have another battery swap it in just because. You May even want to clean all connections with contact cleaner or brake cleaner then using some dielectric grease on the connectors.

 

1c) Especially clean the ecu connectors and the

 

1d) coil pack unit - take it off and also make sure you clean the grounding spots on the underside well. Try replacing coil packs and the base with known good one. 

 

2) Maf sensor. I know you said you replaced it but a lot of aftermarket units are no good right out of the box. If you can try and grab an oem unit from pick n pull... I would grab a couple. see what happens. 

 

3) Vacuum leak. Try spraying brake cleaner around all your vacuum lines and see if your engine changes it's tone at any point (slightly increase/decrease idle or stumbles a bit) you could have a vacuum leak at that point. Pay close attention to inline connectors or right where the vacuum line connects to something, especially if at a T junction.

 

4) TPS is inconsistent/ or have a dead spot/ on unlinear or erratic output. I think this may have been mentioned but was this verified? 

 

5) Loose or bad O2 sensor. 

 

6) What about a bad LIM gasket maybe causing havoc internally?

 

It's late, can't sleep so I put my brain to work a bit to tire it out... Don't know if any of this is of any help, or has been tried or double checked but I wanted to play too... Good luck!

[rben]

Thanks for the effort Chrisssssss.  Most of the things you suggested i have replaced with new or tested them out, except for the LIM gasket.

I think i may have found it. watching the ECM data while driving and some override tests i suspect the TCC is not  working correctly. I found an older "string" in here about the TCC solenoid causing a bucking/jerking effect. When i drove it the last couple days i watched and it did the "thing" when TCC was active. Today i did an override and turned it on and off.  The second it was on it did the "thing" when it was off it ran just fine. The string mentioned something about putting SeaFoam in the trans.  That will be the next thing. If it the solenoid that would explain why all the sensors changed on the engine had no effect on it.

Also can anyone tell me/ show me where the solenoid is?

Edited August 12, 2020 by rben (see edit history)

[padgett]

The TCC locks the torque converter. Be aware that lockup increases the engine load and can make a weak ignition buck.

 

ps  Seafoam has many products. You want the TransTune.

[Chrisssssssss]

Wow... the torque convertor hey... Who'd a thunk it...

 

Well at least you're not spinning around aimlessly now and pointing in the right direction. Always a great satisfaction when you figure something out that has stumped the masses. Now to figure out why and how to fix it. I love seafoam products. They work wonders. TransTune is what I would do too. See how it goes. I also have great respect for the Lucas Oil products. They also have a transmission formula that may work in your favour too. Keep us updated... Good Luck!

[Ronnie]

  

16 hours ago, rben said:

I think i may have found it. watching the ECM data while driving and some override tests i suspect the TCC is not  working correctly. I found an older "string" in here about the TCC solenoid causing a bucking/jerking effect. When i drove it the last couple days i watched and it did the "thing" when TCC was active. Today i did an override and turned it on and off.  The second it was on it did the "thing" when it was off it ran just fine.

 

46 minutes ago, Chrisssssssss said:

Wow... the torque convertor hey... Who'd a thunk it...

 

I'm not on board with the TCC causing the problem. I think the torque converter unlocking is masking the problem by taking the load off the engine. The converter unlocking is doing the same thing as backing off on the gas pedal a little. When the load on the engine is reduced stumbling and/or missing goes away.  I know it gets tiresome hearing Padgett and I hinting at the ignition system causing the problem but most everything said so far points to that or a lean air/fuel mixture.

 

If you want to test your theory of the TCC being the problem just unplug the electrical connector going into the transmission. The connector is right beside the vacuum modulator valve. With it unplugged the torque converter won't lock and the transmission will still shift just fine.

 

 

Edited August 13, 2020 by Ronnie (see edit history)

[2seater]

The two things are sort of intertwined. Our style lockup clutch has what is termed a paper lining and is designed to be on or off with little to no slippage when engaging. Later model tcc’s have more of a fiber lining, similar to a standard clutch, and application can be modulated for a graduated and smoother operation. I think it is possible, at least I have heard in the past, that the clutch can chatter, I think they call it judder, if the lining is defective or perhaps a sticky apply servo. Pretty sure there is a section on it in the fsm which I don’t have handy. The abrupt load on the engine with the in-out style clutch will be more prone to showing an ignition fault. 
 

Have you tried closing up the spark plug gap a little to around .040”?