Rough idle and hesitation at 1300-1700 RPM

[David Dietz]

Thanks for letting me in the group! Okay here we go. 2010 Lucerne 60,000 miles, second owner. I have had it since 49,000 October of 22. Noticed a little hiccup at 55/60 mph about to weeks ago. No engine light. Rough idle. Drops down to 400 sometimes. Before and after I threw parts at it. New coil,plugs,maf sensor,map sensor,purge valve. I also tried a new throttle body assembly. I drove it a few hours and no change. I installed the volt meter tested original throttle body. I replaced the file pump relay. The old one was a little crispy. Took it to the local mechanic shop that's the towns folk swear by and the sprayed throttle body cleaner, changed the air filter and charged me $111.00. So I'm about $500 into this. It's my fault for throwing parts at it but I am at a loss. PS. The shop said it is not a vacuum leak. I am at a loss. And why only at theat certain rpm range? Thanks for your suggestions and comments in advance.

 

[HotZ28]

Welcome to the forums! Has anyone replaced the ignition wires?

 

[2007LucerneCXL]

Not sure if the rear seat fuse box itself was checked as the fuel pump relay was in question there may be additional damage internally, longshot but a possibility.

Not mentioned if a professional scan was ever done, some issues may not set a CEL, or used while being driven. A failing camshaft position sensor is a guess?

 

[ulycyc]

What engine? each may have different unique issues

 

[David Dietz]

Welcome to the forums! Has anyone replaced the ignition wires?

No but that's a good suggestion. I will pick some up this weekend.

 

[David Dietz]

What engine? each may have different unique issues

It is a 3.9.

 

[ulycyc]

Im asking because the V8 has coil on plug setup and no ign wires. As suggested change the ign wires

 

[David Dietz]

Not sure if the rear seat fuse box itself was checked as the fuel pump relay was in question there may be additional damage internally, longshot but a possibility.

Not mentioned if a professional scan was ever done, some issues may not set a CEL, or used while being driven. A failing camshaft position sensor is a guess?

I did remove the dues box and looked for scorching on the wires and connectors. That all looks good under a magnifying glass. But yes there could be a hidden gremlin there as well as the fuel pump. I have 54 psi at the fuel rail and it will sit at 54psi with the fuel pump on and the car not running. I was hoping that would rule out the fuel pump. The car takes off great if you floor it. It just acts like a bucking bronco at 13 to 17,000 rpm while driving normal and going up slight inclines on the way to work. I was thinking of just throwing a cam and a crank sensor at it to see. ?? I wish it would throw a code.

 

[David Dietz]

Im asking because the V8 has coil on plug setup and no ign wires. As suggested change the ign wires

Will do. I thought coil right away at first because I had a 5.4 Triton with a bad pack on plug that acted just like this. New wire will be on it this weekend if not this evening. Thanks for the suggestion.

 

[David Dietz]

Uhg, parked in the driveway tonight and heard what sounded like a bad power steering pump. Nope, the sound got fairly loud and it was coming right from the bell housing. I hopped back in and tried reverse, almost no movement,tried drive barley any movement. Went in the house and pretended not to cry when I told the wife the car we paid $10,000 cash for is really broken. So I went back out after it sat about a half hour,now it's all quiet and I can drive it up and down the driveway. Gotta be the tranny right?

 

[HotZ28]

I assume you have checked the trans fluid level??

 

[David Dietz]

I assume you have checked the trans fluid level??

Yes ,it is right at the top of the marks on the dip stick while idling. Light red in color.

 

[2007LucerneCXL]

This may help on what may be the problem.

Triple Edge Performance

tripleedgeperformance.com

Fluid and filter change, TransGo kit are somewhat a default for the 4T65E. A bang shift after its warmed up is usually a pressure issue, while the lazy shift 2-3 and 3-4 is a TransGo kit fix. Getting a transmission scan may help on identifying what the actual problem is.

 

[David Dietz]

This may help on what may be the problem.

Triple Edge Performance

tripleedgeperformance.com

Fluid and filter change, TransGo kit are somewhat a default for the 4T65E. A bang shift after its warmed up is usually a pressure issue, while the lazy shift 2-3 and 3-4 is a TransGo kit fix. Getting a transmission scan may help on identifying what the actual problem is.

I will do that, thanks for the input.