Isolated incident after dizzy replacement - what could it be?

[Hoesgottaeat2]

Good morning folks,
Been driving my '99 Hoe problem free since putting her back on the road for the season on April 1st. Until last Friday...

I came home from work and parked her. A couple hours later came out to take mama out to dinner and upon startup the engine sounded rough, suspecting a misfire. No SES light at the moment so I drove it up the street, confident I would get an SES light to scan for. And within a few hundred feet the SES light illuminated and began flashing. I turned around and brought her back home to take a different vehicle out for the evening. But before we left in another vehicle I scanned the Hoe and got a P0300, random misfire. At that point I could begin thinking about how I'm going to attack it.

The next day, before I began tearing into things, I cold started the Hoe to be sure it wasn't an issue that's only evident when the engine is warm. Sure enough, an obvious misfire was still present. At that point I went out to my '96 Suburban which I drive in the winter only. During the summer that Burb becomes my parts vehicle as needed lol(seriously). I removed the distributor cap from the Burb and swapped it into the Hoe and voila, the engine was running perfectly again. I cleared the SES light with my scanner and left the Hoe parked in the barn for the weekend. Problem solved, right?

Well, the Hoe stayed parked for the weekend. I did not drive it after the fix until off to work Monday morning(yesterday). Upon coming to my first stop sign about 1/4 mile up the road I had to give her a bit more brake as the idle was stuck up around 1500 rpm. That was the only time it did that. From that point on I have driven it nearly 100 miles with several warm and cold starts and it never did that since. This baffled me as I never experienced that one after a repair like this. And believe me I have made that type of repair several times over the years, this being the 4th Suburban/Tahoe I have owned of this generation.

Knowing all that, my question is this...why the high idle after that repair? Is it possible there was a relearn after I reset the monitors with my scanner? That's the only thing that remotely makes sense to me here at the moment.

Thanks for your input. I really do love this place.

- Nick

 

[Doubeleive]

Good morning folks,
Been driving my '99 Hoe problem free since putting her back on the road for the season on April 1st. Until last Friday...

I came home from work and parked her. A couple hours later came out to take mama out to dinner and upon startup the engine sounded rough, suspecting a misfire. No SES light at the moment so I drove it up the street, confident I would get an SES light to scan for. And within a few hundred feet the SES light illuminated and began flashing. I turned around and brought her back home to take a different vehicle out for the evening. But before we left in another vehicle I scanned the Hoe and got a P0300, random misfire. At that point I could begin thinking about how I'm going to attack it.

The next day, before I began tearing into things, I cold started the Hoe to be sure it wasn't an issue that's only evident when the engine is warm. Sure enough, an obvious misfire was still present. At that point I went out to my '96 Suburban which I drive in the winter only. During the summer that Burb becomes my parts vehicle as needed lol(seriously). I removed the distributor cap from the Burb and swapped it into the Hoe and voila, the engine was running perfectly again. I cleared the SES light with my scanner and left the Hoe parked in the barn for the weekend. Problem solved, right?

Well, the Hoe stayed parked for the weekend. I did not drive it after the fix until off to work Monday morning(yesterday). Upon coming to my first stop sign about 1/4 mile up the road I had to give her a bit more brake as the idle was stuck up around 1500 rpm. That was the only time it did that. From that point on I have driven it nearly 100 miles with several warm and cold starts and it never did that since. This baffled me as I never experienced that one after a repair like this. And believe me I have made that type of repair several times over the years, this being the 4th Suburban/Tahoe I have owned of this generation.

Knowing all that, my question is this...why the high idle after that repair? Is it possible there was a relearn after I reset the monitors with my scanner? That's the only thing that remotely makes sense to me here at the moment.

Thanks for your input. I really do love this place.

- Nick

have you cleaned the intake? the intake and cap/rotor should be unrelated to each other

 

[Hoesgottaeat2]

have you cleaned the intake? the intake and cap/rotor should be unrelated to each other

I have done nothing else. And I agree the two shouldn't be related.

 

[Eman85]

If you're like me reaching the distributor is a stretch and I lean on things. Sounds like you leaned on something a created a vacum leak. More air more idle speed.

 

[Hoesgottaeat2]

If you're like me reaching the distributor is a stretch and I lean on things. Sounds like you leaned on something a created a vacum leak. More air more idle speed.

I lay right over the engine compartment like Superman lol. My chest is still paying for it. The problem resolved itself after that first stop sign. Vacuum leak? Didn’t think of that.

Do these generation computers have a relearn period after doing a reset that you know of?

 

[Doubeleive]

I lay right over the engine compartment like Superman lol. My chest is still paying for it. The problem resolved itself after that first stop sign. Vacuum leak? Didn’t think of that.

Do these generation computers have a relearn period after doing a reset that you know of?

been a while since I had a obs but I would say evap and 02/cat system, maybe egr system also will have to self test a few cycles, shouldn't matter unless you are trying to get it inspected in the very near future

 

[east302]

A relearn is mentioned in the 98 manual, though I’ve never really noticed any issues after clearing codes.

 

[Hoesgottaeat2]

A relearn is mentioned in the 98 manual, though I’ve never really noticed any issues after clearing codes.

View attachment 401825

That’s exactly what I was wondering. I’ll chalk it up to that for now…unless it becomes recurring. So far so good. Thanks a ton for that info.

 

[exp500]

There is a drive cycle completion due whenever power is removed. I havn't seen it required after code clearing. Hope this helps you.

 

[Hoesgottaeat2]

There is a drive cycle completion due whenever power is removed. I havn't seen it required after code clearing. Hope this helps you.

One more thing I did not know. Thank you @exp500.

I'll make sure to NOT tell my wife that I learned something new today. I'm still trying to convince her that I know it all. 35 years and still working on it lol. Wish me luck fellas...