what else for my engine?

[BlazerLT]

Is it a massive misfre?

Or is it just a small studder.

[dtl379]

I think it is a pretty hard misfire. It can vary in strength from time to time while driving, but you can always hear it while idleing. The mechanic has pulled up a random misfire on the diagnostic machine, but no clue as to where it is. It rarely happens while accelerating, but just about always when holding the throttle steady. It can stop when you let off the throttle though. Sometimes it is so hard that I fear the truck will stall on the highway, but it never does. I NEVER have heard any internal engine componants getting banged around, so I guess that is kinda good. Always run an injector cleaner, and check air breather.

I think the TPS needs to be changed also. The truck idles high for about 3-5 seconds when you turn it on. It can also keep the same RPM speed while driving, even though you arn't using the throttle. It sometimes idles irratically and changes speeds very quickly (a change of about 100-150 RPMs) when you stop. It rarely stays at one idle speed for more than 1-2 seconds when stopped. The RPMs most of the time drop to 400 for a second just after you stop, then start the up and down idle. The idle can smooth out, or it can keep going- its not predictable.

We just changed the idle are valve, and cleaned out the MAP and EGR, and checked the MAF. The PCV just got changed, and we changed the vacuum hoses. We had a P0107 code that now is out. I dont know if there is a vacuum leak, but I think so, so we are going to change the intake plenum and throttle body gaskets. But the truck did this long before the vacuum leak.

I dont know if any of this will help. I may have to take it in and have a shop do the high teck diagnostic machine. I just dont want to spend that much on a tech, when it can go for parts. Thank You.

[BlazerLT]

Originally Posted by dtl379

I think it is a pretty hard misfire. It can vary in strength from time to time while driving, but you can always hear it while idleing. The mechanic has pulled up a random misfire on the diagnostic machine, but no clue as to where it is. It rarely happens while accelerating, but just about always when holding the throttle steady. It can stop when you let off the throttle though. Sometimes it is so hard that I fear the truck will stall on the highway, but it never does. I NEVER have heard any internal engine componants getting banged around, so I guess that is kinda good. Always run an injector cleaner, and check air breather.

What plugs did you use?

What was the gap?

What cap and rotor?

Originally Posted by dtl379

I think the TPS needs to be changed also. The truck idles high for about 3-5 seconds when you turn it on. It can also keep the same RPM speed while driving, even though you arn't using the throttle. It sometimes idles irratically and changes speeds very quickly (a change of about 100-150 RPMs) when you stop. It rarely stays at one idle speed for more than 1-2 seconds when stopped. The RPMs most of the time drop to 400 for a second just after you stop, then start the up and down idle. The idle can smooth out, or it can keep going- its not predictable.

The high idle at startup is normal.

The rpms being high when not using the throttle while driving is normal.

What tuneup things have you done again?

Have you cleaned the MAF?

Originally Posted by dtl379

We just changed the idle are valve, and cleaned out the MAP and EGR, and checked the MAF. The PCV just got changed, and we changed the vacuum hoses. We had a P0107 code that now is out. I dont know if there is a vacuum leak, but I think so, so we are going to change the intake plenum and throttle body gaskets. But the truck did this long before the vacuum leak.

P0107 is for the MAP.

Originally Posted by dtl379

I dont know if any of this will help. I may have to take it in and have a shop do the high teck diagnostic machine. I just dont want to spend that much on a tech, when it can go for parts. Thank You.

Just make sure you do a COMPLETE tuneup before you send it to the shop.

[dtl379]

We have tried alot of different brands of plugs, wires, cap, and rotors. Everything from AC Delco to Bosh, to Champion and right now Autolite. These plugs seem ok. It doesn't miss any more, but a little less. Cap, Rotor, and Wires are OE brand. Plug gap set at 0.060, as to spec. Put wire wrap and separators on just in case the spark was jumping.
MAF is spotless. Not a trace on it or in it, and no filaments are broken. K&N air intake kit.

Tune up:
Plugs
wires
Cap
Rotor
PCV
Cleaned air filter
Fuel Filter

Also Changed:
Ignition Coil
IACV
Cam-shaft position Sensor
O2 sensors
Vacuum Lines

Checked:
EGR (cleaned)
MAP (cleaned
Fuel injectors
Throttle Body (cleaned)
Intake Plenum (for cracks or build up)
Spyder Lines

You said that high idle is normal, but it can idle at 2,000 or more. Excpecally after its been started. The RPMs are not that high when driving 65 in fourth gear. They will surge when you put in the clutch, and this all started recently. Is all that normal? I've never seen one do this before. Expecially the irratic idle of 100-200 difference.

[BlazerLT]

Spray TB cleaner through the MAF and clean off the filament wires.

K&N oil will cause the problem and really screws with MAFs.