Surging-stumbling 1990 Reatta

[Edsel-to-Reatta]

Based on advice I was given to resolve a surging-stumbling problem on my newly acquired 1990 Reatta, I converted the Magnavox ignition setup to Delco. Problem not solved. My next guess is fuel delivery...when the stumbling happens, the engine seems starved for fuel. Pressing down hard on the accelerator will often seem to clear the problem temporarily. I will follow the fuel pressure checks in the how-to guides. No idea how long ago the fuel filter was changed, so I will do that job as well.

Edited July 23, 2023 by Edsel-to-Reatta

[2seater]

Good idea to follow the guides👍 

Is the check engine light on?

Do you know how to access the onboard diagnostics?

Fuel pressure gauge is your friend

Is the vacuum line to the fuel pressure regulator wet internally?

[Ronnie]

Drive it with the MAF sensor unplugged and see what difference it makes.

[Edsel-to-Reatta]

On 7/23/2023 at 5:36 AM, 2seater said:

Good idea to follow the guides👍 

Is the check engine light on?

Do you know how to access the onboard diagnostics?

Fuel pressure gauge is your friend

Is the vacuum line to the fuel pressure regulator wet internally?

No check engine light. I read up on how to check the onboard diagnostics, and will go through it. When I converted to the Delco-type ignition setup, I bought a Delco ICM, and cheap aftermarket coils from Amazon. When I drove the car after the conversion, it was perfect. Then the next day it was back to misbehaving. I'm going to return the cheap coils to Amazon, and replace them with authentic Delco coils. I ordered a sparkplug wire set for a '91 Reatta so the wires will be the correct length for the Delco setup. The vacuum hose to the fuel pressure regulator is dry. I assume the regulator has been replaced, because it's a black Bosch regulator.

[2seater]

Bosch brand regulator is stock, so are injectors, I have a set of cheap coils on my setup but I agree it is a good idea to change if it was good and then not It is making life difficult for us when the replacement parts are of suspect quality, even name brands you have trusted for years. Sadly, it could just as easily be the ICM , or something else, but I think you are on the right track to start with coils.

[Ohjai]

the 91 has a test using the Tech 1 where you can chek the cylinders by shutting them down for 3 seconds and measure the RPM at that time..  I don't know if this test is available for the earlier models.

 

[Edsel-to-Reatta]

23 hours ago, 2seater said:

Bosch brand regulator is stock, so are injectors, I have a set of cheap coils on my setup but I agree it is a good idea to change if it was good and then not It is making life difficult for us when the replacement parts are of suspect quality, even name brands you have trusted for years. Sadly, it could just as easily be the ICM , or something else, but I think you are on the right track to start with coils.

After I installed the new Delco ICM and cheap coils, the Reatta performed perfectly including a fast freeway drive. I thought the problem was solved, and then it returned with a vengeance the next day. Perhaps the new ICM from Rock Auto is a dud. The Delco coils purchased on Amazon will arrive today, and I will return the cheap coil coils to Amazon. I bought a can of MAS sensor cleaner and will do that job today. New correct length plug wires for a '91 with Delco will arrive later this week, replacing the wires for the now-departed Magnavox. Fingers crossed something works without too much trial and error replacing costly components. Someone on the Facebook forum had a similar problem, and replacing the TPS cured it. That might be next.

Edited July 25, 2023 by Edsel-to-Reatta

[2seater]

Simply check the TPS for proper voltage at idle (.38-.42) and watch as the throttle is depressed to see if the voltage increases with no dropouts. Over 4.0 volts at full throttle.

[Edsel-to-Reatta]

6 hours ago, 2seater said:

Simply check the TPS for proper voltage at idle (.38-.42) and watch as the throttle is depressed to see if the voltage increases with no dropouts. Over 4.0 volts at full throttle.

Thanks, I'm on it. I need to make up some jumper wires.

[2seater]

6 hours ago, Edsel-to-Reatta said:

Thanks, I'm on it. I need to make up some jumper wires.

Don't the onboard diagnostics work? TPS can be watched directly in ED01

[Edsel-to-Reatta]

4 hours ago, 2seater said:

Don't the onboard diagnostics work? TPS can be watched directly in ED01

I'm new to Reattas, and haven't tried the onboard diagnostics yet. I will read the instructions and try it.

[Ronnie]

25 minutes ago, Edsel-to-Reatta said:

I'm new to Reattas, and haven't tried the onboard diagnostics yet. I will read the instructions and try it.

The more you learn about it the better your life with your Reatta will be. It's your best friend when you are troubleshooting problems.

[derdachshund]

I'll give my 2cents...

Surging/stumbling in my experience is either of 3 things.

1- vacuum leak, really not too many lines on these cars and easy to check, especially the plastic "vacuum block".

2- fuel filter, changed it yet? It's just behind the back of the front drivers wheel under the car/floor where your left foot rests. No tools needed, just a strong pinch grip. Well, maybe a 8mm socket to get the clamp loose.

3- fuel pump, not fun, but doable. Hardest part is dropping the tank and getting that darn rubber flex hose from the filler tube to the tank off. (Getting it back on ain't fun either)

Hope I've given you some direction. I don't think I've ever had ignition problems with surge/stumble. Almost always fuel. But hey, my opinion and 2 cents will get you a soda water at Ferrell's Ice Cream Parlor.😎👍

-derdachshund

[Edsel-to-Reatta]

10 hours ago, Ronnie said:

The more you learn about it the better your life with your Reatta will be. It's your best friend when you are troubleshooting problems.

I did the OBD. The TPS readings are exactly what you said with the key on but engine not running: .38 foot off the gas pedal, 4 gas pedal floored. Does the engine need to be running for an accurate OBD TPS test? The stumbling happens when the engine is warm, never cold.

 

When I converted from Magnavox to Delco, I bought a new Delco ICM from Rock and a set of 3 cheap aftermarket coils from Amazon. The Reatta was absolutely perfect for a day, then the next day it wasn't ok, back to stumbling when warm. I checked fuel pump pressure, good. I wonder if the new Delco ICM went south and only worked for one day? I'm sending the cheap coils back to Amazon and purchased 3 new Delco coils. Waiting for new plug wires, '91 Delco length because the wires for Magnavox are not the correct length for Delco as you know. I ordered a new fuel filter and will change it.

Edited July 27, 2023 by Edsel-to-Reatta

[Ronnie]

On 7/23/2023 at 10:23 AM, Ronnie said:

Drive it with the MAF sensor unplugged and see what difference it makes.

Did you try this?

[Ronnie]

3 minutes ago, Edsel-to-Reatta said:

When I converted from Magnavox to Delco, I bought a new Delco ICM from Rock and a set of 3 cheap aftermarket coils from Amazon.

I think the coils are more likely to be bad instead of a new Delco ICM but you never know about new parts today. I would try the coils first before replacing the ICM.

[Edsel-to-Reatta]

7 hours ago, derdachshund said:

I'll give my 2cents...

Surging/stumbling in my experience is either of 3 things.

1- vacuum leak, really not too many lines on these cars and easy to check, especially the plastic "vacuum block".

2- fuel filter, changed it yet? It's just behind the back of the front drivers wheel under the car/floor where your left foot rests. No tools needed, just a strong pinch grip. Well, maybe a 8mm socket to get the clamp loose.

3- fuel pump, not fun, but doable. Hardest part is dropping the tank and getting that darn rubber flex hose from the filler tube to the tank off. (Getting it back on ain't fun either)

Hope I've given you some direction. I don't think I've ever had ignition problems with surge/stumble. Almost always fuel. But hey, my opinion and 2 cents will get you a soda water at Ferrell's Ice Cream Parlor.😎👍

-derdachshund

1-Will check all vacuum lines.

2-Ordered a new fuel filter and will change. I already checked fuel pressure, good

3-ugh, I hope not. The tank is more than half full, and would need to siphon it empty. Its hard to tell if the stumble is ignition or fuel. Seems to be starved for fuel and won't go faster than 16mph unless I punch the gas pedal then it seems to take off and almost drive normally until the dreaded next stop light, then repeat the stumble.

 

The stumble only happens when the engine is warm, never cold. All seems good for the first few minutes of driving, then a gas pedal press and it stumbles.

[Edsel-to-Reatta]

2 minutes ago, Ronnie said:

Did you try this?

Not yet, but I will try that tomorrow. . I pulled the MAF sensor and cleaned it with MAF cleaner. I haven't driven the car for a few days, waiting on Delco coils to replace the cheap ones and new correct-length wires for Delco ignition.

[Edsel-to-Reatta]

2 minutes ago, Ronnie said:

I think the coils are more likely to be bad instead of a new Delco ICM but you never know about new parts today. I would try the coils first before replacing the ICM.

The Delco coils are made in Poland. I guess that's ok. I'm sure the set of 3 for $30 from Amazon are made in China or somewhere else.

The car drove fantastic after I changed from Magnavox to Delco ICM and the cheap coils. I was all smiles on my first stumble-free drive, good for one day. Bummer the next day wasn't good taking a friend to dinner...kinda embarrassing to show off my new baby. We'll see if there's improvement with the Delco coils...the cheap set is going back to Amazon.

[Edsel-to-Reatta]

On 7/26/2023 at 8:28 PM, Ronnie said:

I think the coils are more likely to be bad instead of a new Delco ICM but you never know about new parts today. I would try the coils first before replacing the ICM.

I installed new Delco coils and returned the cheap $30 set of 3 Mayasaf coils to Amazon. I removed and cleaned the MAF sensor. Then I enjoyed an absolutely FLAWLESS 1 hour test drive on a beautiful summer evening. And then...slight stumbles returned, but not as bad as before. As Ronnie suggested, I unplugged the MAF sensor, and voila the stumbles were gone. Plugged in the MAF sensor, slight stumbles returned. Back in the garage, I noticed I had not re-installed the bellows air duct from the air cleaner to the MAF sensor properly...there was a slight air gap. Maybe that air gap affected the MAF sensor, causing stumbles? With the air duct now properly installed, I will do another test drive tomorrow. If the stumbles return, and unplugging the MAF sensor fixes it, I will buy a new MAF sensor.

 

There is a big price difference between 1990 and 91 Reatta MAF sensors, and I see in photos the sensor elements are different. Are 90-91 MAF sensors interchangeable?

 

I need to get this problem fixed so I can get a smog test and register my newly acquired Reatta.

 

Where is the best place to connect a vacuum gauge to the Reatta engine? I don't see any vacuum hose issues, but want to check vacuum. The previous owner's repair receipts include a new intake manifold gasket.

 

Here is a short video of my perfect test drive. I hear some brake pad squeaks in the video I didn't notice when driving. Brakes are the next project, including replacing the accumulator. Also, the exhaust sounds throatier than I would expect from a Buick.

 

 

Edited July 28, 2023 by Edsel-to-Reatta