Wierd ignition issue? Possibly CAS related?

I appreciate any help trying to brainstorm this issue. I've been so busy lately with work related issues that I cant seem to keep a clear mind and tackle this problem myself.

First start up, engine relatively cool, no problem pulling across the entire RPM range.

After getting warmed up driving the car for a while, if I try to go WOT again sometimes it will just act like a fuel cut/hesitation/sputter/breaking up and wont let me go past a certain RPM (usually somewhere around 4k-6k).

If I turn the car off for a few minutes and turn it back on, the car is able to pull thru the entire RPM range with no problems.

Then after a couple of minutes it pops up again. I replaced the coil/spark plug wire portion of the ignition with a 300m Coil setup and it still occurred. Here is the annoying part. No DTC's show up. Nothing.

Is it possible that it is a CAS related issue? Is something else ignition related that might not be working properly that I should check?

Is it possibly a heat issue? I just need some help on where to start diagnosing something like this. It's pretty frustrating.

 

[ktmrider]

Do you have access to a logger? If so check that you are getting into Closed Loop and/or if the ECU temp sensor is working properly.
You can also check to see if you are getting knock.

 

I use DSMLink. Both closed loop and open look work properly. If by temp you mean coolant, then yes temp is normal. Knock free at 10.8:1.

It just feels like it misfires and doesn't get spark correctly. Defiantly getting air and fuel. Turn it off and back on and the problem disappears for a while.

 

[jackal]

Have you looked at the igniter. When it misfires, what does the tachometer do? Does the needle bounce up or down?

 

Havent checked the igniter. Tach doesnt go crazy tho. It stops at the RPM where it hesitates. I drove it a bit more (4+ hours) and it seemed to really get odd. It didnt want to go past 2.5-3k rpm at this point. I thought maybe thee alternator took a dump but it didnt.

Shut it down for a few minutes and poof it came right back to normal operation. /ubbthreads/images/graemlins/confused.gif

 

Sounds like the ECU is taking timing out!!! You could possibly have the CAS in wrong. Most people don't know this but if you take the CAS out and look at it you will see that it has notches one on the T that rotates and also on the casing. You need to put you engine at TDC and align the notches up together then reinstall the CAS. I think the notches should be pointing to the left or toward the firewall. Had this same problem and this fixed it. Good Luck /ubbthreads/images/graemlins/smile.gif

 

I hate to sound like a simpleton, but how is the condition of your fuel filter?

I had a similar problem.

Changed the filter. Old one had rust coming out of it.

Morale!? Car effing rips like its supposed to, with no timing pull.

Not saying this will fix your car but, sometimes you gotta think "Air, fuel, fire" before your get too complicated. YMMV. /ubbthreads/images/graemlins/dunno.gif

 

[NYC86ZC]

Goose,

what gap are you running on your plugs? if it's too big of a gap you'll have these issues. Trust me, i've been there.

 

Well, I did some testing this weekend. Turns out the ignition and cas are fine.

Had the new downpipe and exhaust put on and found my old readings on the wideband are not the same anymore. So I am now pretty certain all this is related to fuel delivery.

On the way home last night in 5th I decided to try to go WOT from 2.8k rpm. AF's went down like they were supposed to to 10.4-10.8 (for testing purposes). When it got to around 4.4k rpm, the A/F started leaning out to 12.X+++. I went back in DSMLink and tried for shits and giggles to raise the fuel sliders at 4k 5k and 6k to see if it would make any difference. Ran into the same results again.

I hope its just a fuel filter. I will get one this week and try to see if it solves the problem.

If it isnt, what else is left? Fuel pump? Fuel pressure regulator going out? I checked the vaccuum lines going to it.

Would not adjusting the airflow sliders on DSMLink cause the car to still go lean even if I raised the fuel sliders up?

35R in FP housing
1000cc (950) inj
Walbro 255
GM Maft
DSMLink

 

Fuel pumps can behave like this before they die; they work too hard and overheat and draw too many amps and shut down, then when cool can behave normally. It stands to reason that a clogged fuel filter would have a similar result on an otherwise healthy pump, but if the filter doesn't help I'd start looking there. Make sure it's got both good power and ground (is it rewired?).

 

Yup. It's rewired. I will replace both just to be safe.

 

Well, I replaced the fuel filter. No dice. /ubbthreads/images/graemlins/frown.gif

This seems to get worse and worse the longer I drive. It's not only wot anymore either. happens at part throttle too. The longer I drive the lower the RPM threshold before it happens. I drove for quite a bit and I wasent even able to get past 3k rpm even at part throttle today. It would read LEAN on the wideband when it starts stuttering.

I hope its just a fuel pump. I dont know what else would cause this. Can a GM Maf crapping out cause this to happen?

 

[steve]

FPR solenoid is removed?

 

The GM maf is a hotwire sensor IIRC, and if they get oily buildup on them they won't read right and I think read lean. I'm not 100% on that but it certainly wouldn't hurt to clean the sensor. You can get cans of MAF cleaner at autoparts stores.

 

[s_firestone]

Your FPR could be supplying insufficient pressure as the engine RPM increases under load. Might not show up until the engine gets hot.

 

Quoting Qship:
The GM maf is a hotwire sensor IIRC, and if they get oily buildup on them they won't read right and I think read lean. I'm not 100% on that but it certainly wouldn't hurt to clean the sensor. You can get cans of MAF cleaner at autoparts stores.




Out of curiousity, I was going to rotate my MAF 90 degrees so the bars are parallel with the ground and found this when looking at the backside.

Good ol water/alky puddled on the bottom (white spot area) and all over the bar near the hot wire. Not the smartest tool in the shed but im pretty sure this would cause some if not all of my issues. /ubbthreads/images/graemlins/uhh.gif

I guess i'll just yank out the injection system for now and just run good ol pump gas.

 

Cleaned the sh*t out of it with MAF cleaner. Same thing. This is fuel delivery related, I'm definite about it now. It's either the fuel pump, fpr, or the line itself.