Midnightevo8

iTrader: (6)

For the past few years I have had a jitter problem. It started with a new build which consisted of a 2.1 destroker, gsc s2 cams and fp red on e85 w/ tephra v7 sd. I drove the car on MAF to break the motor in for a few hundred miles with no driveability issues whatsoever. Before getting the car dyno tuned I switched everything to run SD. The car was tuned and map switched to SD rom by Chris Black at AMS. The tune went smoothly for the most part but when taking the car for a drive I experienced my first jitter issue. I noticed a very jerky almost hesitation when at very low throttle and ranging widely from low rpm's to around 3,000 rpm or so. The problem is at its worst when trying to maintain speed on the highway or while cruising at a constant speed, almost like cruise control. The problem has been there for 3 years but I have learned to live with it as I tried several possibilities to fix the issue.

As I slowly continued to build and further modify the car some things were changed that could rule out possible scenarios. Most recent build included full 6466 kit still on e85 and SD

The car has also been tuned on 2 different occasions. Recently was tuned at Evolution Dynamics on my current setup and the problem still persisted.

Solutions tried to fix problem:
3 different ignitions, 1. Buschur COP w/box. 2.Spoolinup Coils 3. Now currently running stock.

Went back to maf.....didn't fix

Compression is great across the board.

Spark plugs, copper bpr8es and also iridium same heat range.

FIC 1450 injectors but now running 2000 cc high impedence FID injectors.

swapped out map sensor with a known good one

replaced cam sensor from advanced auto

Logged timing advance, ipw, voltage, tps signal and afr's and everything seemed normal.

I'm away from the car and just trying to get this post finished up. I can report back with any details as I'm sure some of you will have questions and advice for me to try. Thank you in advance for your time, it is greatly appreciated.

Charlescrown

I am surprised you didn't take it straight back. Jitter as you say is probably surging caused by a lean fuel mixture. You need to fit a wideband and take it for a cruise. If all is OK it should read the expected 14.7:1 or there a bout's. If it's leaner you need to retune.

LetsGetThisDone

iTrader: (1)

Seems obvious, but, are the jitter fixes enabled in SD programming?

Benja

Log your RPM, TPS and IPW whilst constantly cruising.
When 'jittering', you'll see the IPW bouncing round a fair bit more than normal, its a SD rom issue.

Midnightevo8

iTrader: (6)

Sorry for the delayed response. I have been rather busy but should have more time today and tomorrow try different options. I really want to get this issue resolved so that I can actually enjoy driving the car again. The car already is a pain to drive with all the mods and quartermaster clutch let alone it misfiring while cruising. But nonetheless Because Racecar... haha

ROM Info: The Rom ID is 94171715

The car was tuned by on 3 different occasions and none of the tuners were of much help, when asking to locate the issue I guess they assumed it's a mechanical issue outside of the tune.

I have tried all 3 jitter fix options in ecuflash. Didn't notice much of a difference. I will try them all again if they seem to do the trick.

I do have the AEM w/b installed. The stutter seems to happen regardless of afr's.

Benja: I will try logging the suggested values and post back results as soon as I can.

Thanks again to all of you for your help.

Charlescrown

I am surprised that the problem does not show up on a wideband. If the mixture is lean it should show and if the ignition missfires it should also show up. Please do a log and post it. This one is what I call outside the square but be patient.

LetsGetThisDone

iTrader: (1)

Enable all three jitter fixes..