Plugs bad already?
 

Put a fresh set of plugs in with my rebuild. The car ran for about two weeks (85 miles) in limp mode due to a knock sensor issue. After the third day I started to get a slight stumble at low rpms, most noticeable at slower speeds. Felt like a misfire really. It got worse slowly. Now my knock sensor is fixed and limp mode is gone, but the stumble is still there and getting worse and more common. Today it was to the point where cruising at 25 mph the car stumbled and bucked as soon as I released the clutch to accelerate. Would idle fine but would not start from a stop. Shut the car off and started it back up and it was fine. Im thinking maybe my plugs are toast from running in limp mode so long. Any thoughts? I searched but couldn't find something so specific.

Had no issues this morning (0500, 4 mile drive). Seems as I have issues in the afternoon once it gets 80* plus here at Camp Lejeune.

what ecu are you running? with a new build the motor may be running too rich or to lean when at temp. also what injectors are in the car? there is a large list of possible reason for the stumble, lets try to narrow them down.

^My guess would be stock computer due to the OP mentioning limp mode.

Is this car a DD? Why would you drive it for 2 weeks in limp mode?

Why dont you just pull the plugs and see? Is the idle smooth? What RPM?


John

Double post

You might want to check out post #42 (and subsq.) in this thread.

Yes stock ecu and injectors. I didn't really have a choice as to driving in limp mode, my dd was in the shop. Idle is smooth but sometimes higher than normal (1100 rpm). I've got plugs coming tomorrow as a starting point. I'm also gonna check tps voltages as a start.

Thanks for the help guys

This has alsO peaked my interest so this weekend I'm planning to add some 8 gauge grounds. Thanks!

Update: changed the plugs and the problem is still there. Going to source some 8 gauge wires for grounds and try that.

And temp is not a factor as it acted up this morning on the way to work.

check your wires.... also ive had the same problem (went through two plugs after a rebuild) running the car rich will do that to them.. be very careful not to richen out the car.

Had some known good wires and set of coils so I swapped those in. Also added some grounds. Negative terminal to shock tower; shock tower to coil/rats nest rack, there to upper intake, intake to firewall. About to go for a long test drive. Results shortly....

Took a couple shorter drives. Issue seems close to non-existent. Hopefully it's gone. Next step is power fc, block off plates and a tune.

Still doin it. Fml

Did you do the stuff linked to in post #6 above? I know you added grounds, but did you fix the ones already there?

Possibly an intermittent TPS issue

I went through all the grounds in the engine compartment. Cleaned them up, then added a couple more.

My tps has two Phillips head adjustment screws. I'm having a fun time trying to get to them, I need to get a 1/4" drive ratchet to get at them as my 1/4" to 3/8" adapter is too long.

I also have an extra tps (cough..thanks chris...cough) incase this one is bad.

Honestly from reading your other thread, it sounds like you have a crispy engine harness, this would be the cause of countless issues.

I agree 100%. Its on my list of things to change out. Even if its not the cause, its a ticking time bomb with as brittle as it has been. Im sure the price of a new oem harness is pretty high. Ill probably do a new harness when I do my Power FC and blockoff plates. I may get in touch with you guys to do some work for me shortly.

I searched that other thread and found the service info on bad stock grounds. Cleaned up those and added another ground from the lower harness ground to the fenderwell ground I added previously.