Intermittent engine miss problem

[6 to go]

I have been fighting this problem for ~ 10 or 12 years now!
It misses at cruise, starts good, pulls strong, doesn't die, but will
miss and maybe run a few minutes and miss again. It doesn't miss
at idle. Doesn't seem to miss pulling hard.
I have installed new crank sensor, cam sensor, battery cables, cleaned ground
points, new plugs (several times), new plug wires (several times), new coil/coil
packs ( several times), cleaned the injectors, installed a new injector harness,
different ECM's, new 750 CCA battery. Multiple mechanics have had the car,
none solved the problem!
Can anybody offer any ideas? Help, please!

 

[captflash]

Subscribed. I have the same issue.

 

[TurboBuRick]

Does it do it in batch fire?

 

[6 to go]

The engine misfires after it is fully warmed up and cruising.
Not when it is pulling hard, but @ part throttle.

 

[Casey Jensen]

Check your plug wires. When it's missing at idle, carefully take insulated pliers and start moving your wires around. I was having the same problem. Only problem, I used my bare hands! Wow that ignition packs a punch. I thought I could wiggle the wires around to see if it I had a bad wire and get it to arc to ground.

 

[precizion818]

Check your plug wires. When it's missing at idle, carefully take insulated pliers and start moving your wires around. I was having the same problem. Only problem, I used my bare hands! Wow that ignition packs a punch. I thought I could wiggle the wires around to see if it I had a bad wire and get it to arc to ground.

Lol..... been there, done that

 

[whitehot1]

What chip are you using? Do you have a scanmaster and if you do can you post all the numbers with the engine warmed up.

 

[Phoneguy]

Have you pressurized the TB with the valves closed to see if the intake is leaking? 10-12 years is a long time to let this go...

Bryan

 

[Boost231]

module?

 

[TurboBuRick]

The cam sensor setting can effect light throttle cruising as well.

 

[jasjamz]

The cam sensor setting can effect light throttle cruising as well.

Yep... he should start the car, unplug the cam sensor and go for a ride. See if the problem stops.

 

[wilkinsde]

I had the same problem as described a few years ago with the first GN owned. We had upgraded to 42lb injectors along with other performance upgrades. Changed a bunch of things out trying to eliminate the intermittent miss. Finally put the old stock injectors back in and the miss went away. One of the 42lb injectors must have been defective. Should be considered as a possibility...

 

[whitehot1]

I had the same problem as described a few years ago with the first GN owned. We had upgraded to 42lb injectors along with other performance upgrades. Changed a bunch of things out trying to eliminate the intermittent miss. Finally put the old stock injectors back in and the miss went away. One of the 42lb injectors must have been defective. Should be considered as a possibility...

So did you ever have the chip and injectors tested to determine which one was causing the problem?

 

[6 to go]

Igntion wires changed several times. New wires on it now.
Injectors sent to PTE and checked and matched w/i 5% of each other.
I just have a scan tool, so no #'s.

 

[6 to go]

BTW, this is the 3rd cam sensor. All were set with Casper's cam setting tool.

 

[wilkinsde]

So did you ever have the chip and injectors tested to determine which one was causing the problem?

We did not test the injectors, just assumed one of them was defective when the stockers were put back in and the problem went away. The 42lb injectors were purchased from Poston's. I returned them for a refund, bought a chip and 60lb injectors from Turbotweak; performance achieved with no intermittent engine miss at part throttle.

 

[dand]

Look into replacing the vehicle speed sensor (vss) if its original.

 

[TurboDave]

Could be a bad spot on the TPS??

 

[6 to go]

Car has missed with more than 1 TPS on it.
The VSs is a new one and no, I haven't replaced it.
Will it cause an intermitten engine miss?
It will only miss @ part throttle cruise.

 

[TurboBuRick]

It's likely ignition related. They are very finicky on these cars. Aftermarket components will cause these types of problems too. Is everything ac delco? Module, coil, cam and crank sensors?

It could also be lean in that area of the tune. Take note of your blm's during the condition.

RL