1997 Engine / Transmission Problems

[rcman989]

Baffled at 1997 Engine / Transmission Problems

I have a 1997 K1500 with V8/350. It has a Black Bear Performance tune, headers, and a cold air intake. This past winter it started to stumbles/bogs down/hesitates when I accelerate from stop, when at a stoplight sometimes at idle it will almost miss but it doesn't. I changed the spark plugs, wires, cap, rotor, coil, and fuel filter. It ran fine for a while after that, but tonight it did it again really bad. The codes showed misfire on cylinder 7, random misfire, and had a P1621 code which I have never seen before. It would accelerate fine when you really stepped on the gas, but when you held it at 55 it would hesitate, seems like it would try to shift, backfire, and had no power. I am assuming it is not transmission related because at a stop light it wouldn't idle right.

Any suggestions? Thanks in advance.

 

[rcman989]

Bump for some help. Got an 8 hour drive coming up Thursday and I hope it can be fixed before then.

 

[polar]

Did this all start after the tune? I know there are some rare occurrences that the PCM was ruined and I think that is what that code refers to


Sent from my iPhone using Tapatalk

 

[rcman989]

Nope this had happened before the tune.

I forgot to mention I did an EGR delete before the tune and had the EGR tuned out after the tune. So I was thinking after the tune it should help it since EGR is tuned out, but this was not the case.

 

[Big D]

I searched P1621 on Shop key and it says that code doesent pertain to your truck

I Also searched it on Engine codes.com and it also says it doesent pertain to your truck.

I think polar may be on to something.


http://engine-codes.com/p1621_chevrolet.html


was that code running before the tune?

 

[96Z71ECSB]

Alldata doesn't show P1621 for your truck either.
I second the motion that polar might be on to something.

 

[SAATR]

What's your fuel pressure?

 

[polar]

What made me think it was the PCM was that the code didn't register for our trucks when I looked online. Then I started reading about what the code meant. Some people said tunes screwed up their PCMs due to various reasons. Most of them tried cheaping out on tuning. If your PCM is bad, I have no clue how someone could test it. I might have an extra laying around if you need it, I can work out a deal with you.

 

[rcman989]

I know it can't be the tune because I had the exact same bogging / hesitation problem before the tune. I was hoping the tune would help fix the problem because I thought the EGR delete was screwing it up. I did clear the codes and pull the positive on the battery and after that it has ran fine. I also noticed if I accelerate in drive and then when at cruising speed shift into overdrive it was fine. Just confused why it will do it one day and is fine the next. If it was fuel pressure related can it vary from day to day?

 

[bobfig]

sounds like a CTS or bad fuel pressure.

when i had my 4.3l it seems to drive fine but acceleration would suck balls and wouldn't want to get over 60mph or what ever it was unless your going down hill with a tail wind for over a mile. drove that on a 2 hour trip. that was a CTS problem. now another thing is it drove ok while the engine was cold but once warmed up it was a dog.