Please, I need your expertise!!

[GN18944]

Symptom: Slight misfire at cruising speed and idle.

Here is what I've ruled out:
-EGR valve (vacuum pump tested)
-Injectors (tested)
-Coil pack resistance (new and tested)
-Spark plugs (new, 2 sets)
-Plug Wires (new)
-Compression (150-155 on every cyl)
-IAC numbers (21)
-TPS numbers (.44)
-Fuel Pressure (42 line off)
-Vacuum leak (mostly new lines, 19lbs at idle)f
-Weak valve spring (vacuum holds steady and does not fluctuate at idle)

I've only owned the car for a few months, the only other unknown is when the chip was purchased, before or after the new injectors were in place. I ordered a new chip this evening to rule out a timing issue with the larger injectors.

My only other thought is possible a sticky valve? I thought this was unlikely but possible. I'm just not ready to rip the heads off yet.

Who has ideas!?!?! I have access to the tools necessary for just about any diagnostic process, I'm just running out of ideas.

 

[87-WE2]

I had the same issue with mine with an old ATR Pitbull chip. Right around 45 mph if I remember. Got a new turbo-tweak chip and it fixed it.

Might be worth it to pull the TCC plug from the driver side of the transmission and test drive it. I was told that if the TCC solenoid fails it could cause what feels like a miss. By pulling the plug for it, it keeps the converter from locking.


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[GN18944]

I had the same issue with mine with an old ATR Pitbull chip. Right around 45 mph if I remember. Got a new turbo-tweak chip and it fixed it.

Might be worth it to pull the TCC plug from the driver side of the transmission and test drive it. I was told that if the TCC solenoid fails it could cause what feels like a miss. By pulling the plug for it, it keeps the converter from locking.


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Glad to hear I may be on the right track with a new chip *fingers crossed* It happens and idle and in any gear with very light throttle, I don't think it's a torque converter issue.

thanks for your feedback!

 

[TurboBuRick]

Stock maf? What's the bl running. Get the bl number at idle and light throttle cruising.

While you're at it, post all your number engine warm @ idle.

 

[SPOOLFOOL2]

Check your cam sensor. Make sure that the tab didn't break off inside and let the ring spin.
Let us know what you find. Any "MAL" codes on the scanmaster?

 

[Chuck Leeper]

Diagnostic tools include a Powerlogger? If so, do a log, and see if anything pops up.
Voltage fluctuations?
Cleaned and inspected all grounds?

 

[forcefed3.8's]

Cam sensor not set correctly will cause a random miss at cruise.

 

[GN18944]

Check your cam sensor. Make sure that the tab didn't break off inside and let the ring spin.
Let us know what you find. Any "MAL" codes on the scanmaster?

How do I check the cam sensor?

No MAL codes

 

[SPOOLFOOL2]

How do I check the cam sensor?

No MAL codes

#2 phillips screwdriver. Remove the cap and see if the ring spins. It should not spin. Don't force it and break the tab.

 

[blackazz]

What style maf are you running?an how old is it.

 

[Chuck Leeper]

Diagnostic tools include a Powerlogger? If so, do a log, and see if anything pops up.
Voltage fluctuations?
Cleaned and inspected all grounds?

KTBregal.. What's with the "old" rating on this post?
I'm old, but don't need to be reminded...

 

[Ktbregal]

I didn't rate this post.

 

[SPOOLFOOL2]

I didn't rate this post.

Actually, you did.
But don't worry. I agree with you. Chuck ain't no spring chicken ya know.
However, it was a pleasure to meet him at BG.

 

[GN18944]

Stock maf? What's the bl running. Get the bl number at idle and light throttle cruising.

While you're at it, post all your number engine warm @ idle.

stock MAF, bl's are steady around 128. Weather is less than fortunate here today so I won't be driving it today unfortunately. I will however have time this afternoon to check out the cam sensor.

 

[GN18944]

Diagnostic tools include a Powerlogger? If so, do a log, and see if anything pops up.
Voltage fluctuations?
Cleaned and inspected all grounds?

No voltage fluctuations. very steady charge. However, I have not cleaned the grounds.

 

[Ktbregal]

Sorry guys but I didn't, don't know how and I would like to know how it happened without me????

 

[GN18944]

Stock maf? What's the bl running. Get the bl number at idle and light throttle cruising.

While you're at it, post all your number engine warm @ idle.

Had a chance this afternoon to run it a bit. Here are the numbers:

02's in the mid 700's
L8 37-39
Int 128
BL 126
Ats 68
TPS .44
IAC 24
cc 121

 

[GN18944]

How do I check the cam sensor?

No MAL codes

The ring does not spin and it has very little play in it.

 

[Chuck Leeper]

Sorry guys but I didn't, don't know how and I would like to know how it happened without me????

MAGIC!!

 

[GN18944]

I'm not sure if this means anything or not but I drove the car with the cam sensor unplugged and it did not change the misfire. With my basic understanding of batch firing I'm assuming this means nothing if the cam sensor itself was installed wrong.

I'm not sure how clean it typically looks inside the cam sensor cap on a 30 year old car but this was remarkably clean. Thanks again for everyone for your help, this is beginning to get quite aggravating but I'm determined to find the issue!