Installed a 2.9, 42 lb inj., two step colder irridiums, and stage two belt. Got it custom HPTUNENED by 04REDLINE from the redline forums.

My IAT2 temps are normal, the engine knock has been all worked out, but I am getting a major surge or pulsing from 90+ mph in 3rd gear. If I shift into 4th, it continues going past 90 mph without a hitch.

Heres my HPTUNER LOG for your reference. http://www.geocities.com/lordfatal1/...hptunerlog.zip

Thank you

 

For starters, your plugs are too cold. Get one stage colder, and retry.

 

I would put the copper NGK's in there and see how that works out..try gapping between .035 and .030 every car seems to act different to the gaps

 

Im the guy who tuned him.
I advise most guys here in Cali (due to our lower octane level and hot weather) to automatically swap to 1 stage colder stock. Steven here is using stage 2 colder plugs and they are all gapped at .35 as well as had his spark dwell modified to help with the spark blowout, just in case. Ive run this setup before on a few other stage 2 + cars, without issue. It seems to me the issue might be Injectors going static, although the injector's duty cycle barely breaks the high 80s low 90s at 6300 rpms. Im thinking that, or maybe his MAF/air filter might be dirty. Also the hp tuner logs are up for all your viewing pleasure. Thanks again to all who have helped, and will help in the future.

 

Bump!!!

 

2 steps colder seems like an awful lot. The car actually depends on reaching certain tempuratures in the combustion chamber to operate effectively.

You say you aren't getting any knock when you get the "surging"? Have you logged the car when the surging is occuring? Perhaps one or more of your injectors is going static?

 

Your commanded air/fuel ratio is all over the place causing timing to be randomly added or removed at WOT.

 

The commanded air fuel is straight form the gm stage 2 tune. I havent done any modifications to his maf at all either, since he still on a stock intake system.
Hmmm, think MAF tuning is going to be in order?

 

forgive me, you tuned him, and left his WOT A/F alone?
i think maf tuning can never hurt, depends on your customers budget methinks.

 

sounds like injector problems, i had the same thing happen to me, feels a lil hesitant, or like the car sputters, then after a second car goes back to norm.

 

Not at all, hes running a stage 2 map. Nothing more. His mods are 42s and 2.9 pulley.
On top of that he knows about me not bieng able to tune his fuel correctly without the use of a wideband 02 sensor. LOL@customer remark, its all good, me and him are buds, so i was just trying to help him out. Thanks for the comment though.

According to the log i have wiht my config, the commanded afr seems to be fine. The timing advance also looks normal as well. ramping up at .5 increments at a time.

 

sorry, i was overly assumptive.
so you were just wiping his KR, and tweaking his timing/ tq mgmt.?

 

Yes sir, in that log u see he knocked a bit from his second to third shift. i fixed that as well. Normally if theres a wideband, ill tune just about everything i can. I by far know im not the best tuner out there. But id like to think im not the worst. My assumoption for his car is air filter, it may have a breathing issue. His car has 17k on the clock with the stock filter...I will keep you all posted on this issue, he will be coming back out tommorow.
Firestorm, no hard feelings on the assumptions, i knew you ment it in a respectful manner

 

when i get home i'll look at the logs on my home computer, post a copy of the tune if your willing

 

Cobalt SS stage 2 tune. If you need a copy of it lemme know.

 

no CEL'S when it's surging???

 

No sir.

 

i'll take a copy if it's an unmodified version.

 

stock stage 2 and a 2.9 and stock plugs no problems i ordered 1 step colder for the 2.8

 

Steven will post the tune up for ya Jimbo, he has a place to store them. should be up shortly

 

there are copies of stock stage 2 on the hpt sopository.

 

from what i heard it have been modified a bit.

 

its ur plugs...i had the same problem since i was using 2 step colder as well...one i put the stockers back on,car ran like a champ

 

i know he is running California 91 **** water.. maybe the 2 step colder is alittle to cold? i mean **** i see so many people doing the stage 2 with 2.9 on the factory plug's.. and the colder step plug's is to help knock right? he need's to log it when it happen's so we can really see what's going on..
and BTW steven i saw you at the downey yesturday. i was with my grandma.. and i noticed somthing while leaving.. you got a sick ass hood on your car.

 

Were going to try everything to get it fixed tomorrow, since hell be coming down. Were going to go thru a process of elimination, and will inform you all of tomorrows outcome.