I recently took my car to a referenced mechanic for coil packs. I now have a problem that the mechanic cannot fix and just shrugged his shoulders and basically said I cannot do anything more. When the car excellerates to 3,000 rpm it misses and I am unable to excellerate thru this range.
Here is a list of newly replaced parts:
Plugs
Coil Packs
Upper intake gaskets
Upper & lower plenum O rings
Smoked tested for vacuum leak = undetected

I have bit the bullet and made an appointment with the dealer for Thursday. Any thoughts on the cause? If I can avoid the whopping bill I would like to. The mechanic claims its a computer problem.

Also they had to put an insert into the intake as one was stripped.

Thanks in advance! Runs like a dream until you excellerate to 3,000 RPM.

Doug

 

Doug, sounds like your car is in limp home mode. There has to be a check engine light on the dash and a stored code. Get the code read. I would have to guess your mechanic had done that already. If so, post the code here or do a search of the code number here. Chances are it has been talked about and diagnosed. If your mechanic cannot read the code, I would get a different mechanic. Without knowing any other particulars my initial guesses would be the lower intake gaskets, the throttle body or the MAF sensor.

By the way, welcome to the forums. When you get a moment go to the new members section and introduce yourself. It is a requirement here. You have come to the right place. You won't find a friendlier, more helpful site on the internet.

 

Alfadude,
Thanks for your help. He did read the codes and I also forgot to list additional parts.
The codes were: P0171 & P0174 (Too lean bank 1 & Too lean bank 2)
He also replaced the MAF sensor and cleaned throtle body.

I did notice that one of the intake manifold gaskets was different than the rest of the new set once he removed the intake for a second time. Would it be possible that could be an issue?
All suggestions welcome. Thanks everyone.

 

I had a similar problem due to the rear cat being clogged, my mechanic had me pull the rear upper O2 sensor, keep it electrically hooked up and take it for a drive... she ran fine because the back pressure was gone... free but a bit of a bugger to pull if the heat shields are still in place
HTHs
Gary

 

Looks like there is still a vacuum leak. PCV hose (split underneath unless it's the reinforced ribbed one) & Brake Booster check valve (look for deterioration especially if it's the old white one) needs to be looked at as well. Can't remember if my smoke test specifically revealed that one.

 

Magically, this morning I started up with no check engine light. Car runs as normal no issues. Revd up to 4,500 rpms ran as normal. Would this rule out a vacume leak? I mean leaks are not intermittent right? Considering the long list of new parts including MAF could it be an O2 sensor. Do these work intermittently or just fail?
After driving 10 minutes check engine light came on and same problem occurs at 3,000 rpm. Still baffled.
Doug

 

Those codes signify a vacuum leak. I would not rule that out as it could be that it is intermittent and only be present if something expanded from heat as you drive it. As Mohrd said, check the brake booster check valve and the PCV hose. Also the lower intake gaskets. Do a search on here regarding those codes and you will find plenty of postings about it and how to fix it. You don't say where you are located. If it is a cold weather climate with all the cold weather it isn't uncommon to have these kinds of things pop up in the extreme cold. I know it is frustrating, but it is probably a relatively simple and inexpensive fix. Hang in there.

 

I am still flumoxed with the same problem even after the dealer found the vacuum leaks. Dealer recommends lower gasket seals replaced at $550.00. I don't think thats the issue. Last OBD scan read 0174 too lean bank 2. So we succeded in solving code 0171 with the vacuum leaks.
The same dead miss at 3,000 rpm occurs at 27 degrees start or start and drive in 70 degrees. It does not seem to be a vacuum heat and expand issue. has occured from dead cold start as well.
I have noticed that intermittent start and drive the engine has a god awful chattering, metal on metal clanking, diesel sound and then check engine comes on and cannot accel past 3,000 rpm again. Other times there is no such engine noise and she runs like a dream. No miss smooth accel past 3,000 rpm. Could this mean its an electrical sensor issue.
Recap of parts replaced:
MAF Sensor
Plugs
Coil Packs
Upper intake gaskets
Upper & lower plenum O rings

What sensors effect the fuel air mixture? Could it be a faulty part? (MAF) or O2 Sensor? I have not changed the O2 sensors and wonder if one is failing at times.

Is this logical train of thought??? I hate to pay that kind of money on the basis of process of elimination.

Thanks for your input.
Doug

 

A better question may be which ones don't.

 

Mine did that when the knock sensor went bad.