Studdering and shifting problem.

Howdy,

2000 Buick PA with 60,700 miles. New problem. A few days ago on a warm summer day (low 80's) after driving around town for 1 plus hours and maybe 15-20 miles I notice the car was studdering and shifting up and down at lower speeds.

So today I took the car on about 5 mile drive. I took it to a hill close by the house. I drove up the hill twice. When the engine is cool no problem and the trans did not shift up and down but stayed in the correct gear to go up the hill at around 28 miles a hour. I did the hill twice and all good as no shifting or studdering.

When the car warmed up to operating temp I did the hill one more time. The trans shifted up and down maybe 4 or 5 times on the 300 to 400 yard incline. So the car only acts this way when the engine is warmed to 170 degrees. Stop and go driving it will studder and stall just for a moment. Also one time the rpm's in park where 1800 when hot.

I did put new Autolite AP606 plugs in about 5000 miles ago. Also has new ACDelco 7mm plug wires. Local auto parts checked coils and ICM and tested okay. But neither ICM or coils were hot when tested. One more thing, I am not getting any yellow check engine light.

So anything I can check to try to find this problem. Thanks for any help in advance.

I hate to be the one to break the news, but the wires you installed are pure junk. Don’t feel bad, our shop made the same mistake about 6-mo months ago, when we reluctantly installed a set of ACDelco 7mm (Part #746DD) wires on a '95 PAU the customer purchased from Rockauto at a huge discount. Within 2-months, the customer returned complaining of shuddering/stuttering under load, only when the engine was at full operating temperature. After scanning, we found a pending random misfire code (P0300). The techs first guesstimate was, since the wires were new, that could not be the problem, so he focused his diagnostics on the ICM/coils & plugs. We had a spare ICM with all new coils that he installed and the problem persisted. (again, only @ operating temp).

Next, the customer wanted to install a new set of NGK Iridium plugs (which we did) again, without any improvement. After all this work, the tech was beginning to get frustrated, so he asked for advice. I walked out to the shop floor with him and asked him to start the engine. When the engine fired, I immediately heard the sound of misfire from the coil towers to ground. I told the tech to turn the engine OFF & change the wires. He said "but they are new wires, that can't be the problem"! I went to get my DVMM to check the resistance of the wires. I found two of the front bank wires ( #1 & #3) were infinite (0 ohms). I did not bother to check anymore, just removed all of them and threw them in the trash. The tech installed a new set of Belden 8.5mm wires (Part Number: BEL 69401) $95.00 from NAPA and the problem was solved.

Last week, the same customer stopped by to get an estimate on a brake job and I asked him if the engine was still running good. He said it has not stuttered once with the new wires. He also mentioned, “he learned his lesson about buying cheap parts for his car.” :smile:

Hotz28,

I'm a little confused. The reason I went with acdelco 746dd 7mm wires is because I read maybe four or more post by mods and others in this forum that acdelco plugs and wires were the way to go on gm motors. A few other brands including Belden were also mention.

I did check with my loca Napa and was told the only Napa Store that had these Beldon 69401 Wires was in Kansas City. I live in Washington State. Local store did have other Beldon Wires for around $34.00.

I thank you for your time and advice. I always try to buy good replacement products for my Buick PA. Now I am not sure about acdelco parts. Is it just the plug wires. :confused:

Some of the older threads may have mentioned ACDelco 8mm wires as one of the best replacements. I am not sure what happened to ACDelco wires, but like many other parts, they were probably outsourced to Mexico, or China. Check the resistance on each wire, then let us know what you find. Be sure to flex the wire when testing to look for a resistance change.

Some of the older threads may have mentioned ACDelco 8mm wires as one of the best replacements. I am not sure what happened to ACDelco wires, but like many other parts, they were probably outsourced to Mexico, or China. Check the resistance on each wire, then let us know what you find. Be sure to flex the wire when testing to look for a resistance change.

Thanks for your reply. I have not check spark plug resistance yet. But I did follow your advice on checking the spark from another one of your posts. So I used a extra spark plug gapped to 200+ and checked the resistance on the 1/3/5 coil hole. I saw very little blue spark but a lot of yellow spark. Last week I did have a parts house check the ICM and on their machine it checked out okay. But I would think the yellow spark on all three coil holes would mean the ICM is bad.

Yes the acdelco 746dd wires were made in Mexico.

So I guess I would need a new ICM.

Thanks for any advice.

No, you do not need an ICM. An ICM has nothing to do with coil output voltage . Did you test spark with existing wires?

No, you do not need an ICM. An ICM has nothing to do with coil output voltage . Did you test spark with existing wires?

Okay I finally got back to check the spark plug wires. I only checked the front bank. No. 1 had 1.464 ohms, no. 3 had 2.112 ohms and no. 5 had 2.497 ohms. The spark from these plugs had a narrow long white color that had a little blue on each end of the spark. Also after I drove car to test engine again still had the same symptoms. But hot motor seem to have a somewhat of different slight smell. Maybe a burn smell. Wish I could describe smell better. Also when I started car up yesterday I got a P0300 code in the first 10 seconds.

Also the problem is a lot worst when the motor is warmed up.

Thanks again.

My PA has been fixed. I took PA to a independent repair shop. They are very familiar with GM Cars. The problem was a frayed, damaged wire in a wire hardness close to the starter motor. Tech found p0102, p0122, p0134, p0452, p1122 and p1635. Tech replaced bad wire with a good wire spliced into harness. Cost one hour to diagnose problem and 1/2hour to fix. Charge for repair was $150.00. PA runs very well now.

What did I learn even at my senior age is don't wait so dam long looking for the problem. From now on I will check the easy things and then take it to my new repair shop if I can't fix the dam problem. :). :)

Thanks for the feedback, and I am pleased to here your shop found the problem. I assume the frayed wire originated from the CKPS; even though, this not a common occurrence, sh*t happens.