3800 Car shudders under part throttle

[imported_Diavolo]

My car has started shuddering under part throttle. I thought it was misfires so I changed the plugs (from tr6 gapped at .56 to autolite 103 gapped at .52) but the problem remains. My LFT's will shoot to -30 (didn't know they could go that low) and my boost will shoot up to 10psi.

The only thing I can think of is I installed a S2 ZZP TB and it has no MAF screen. I have a wizair intake as well.

I am assuming that is the problem, but didn't know since a lot of people run without the screen in with CAI's.

If anyone has any insight that would be great

Thanks
-Mike

Click to read more...

 

[alexgtp]

WHat are you Ltrims at idle ?
and IAC ?

 

[imported_Diavolo]

at idle my LFT's are 0, at cruise they are between +2 and -2 (I have ICCU). My IAC I havn't checked. Should I check at idle and cruise?

 

[imported_Ron Vogel]

I'd assume the maf might be causing this. I'd scan the raw maf frequency, a ported tb should run you lean at idle, then rich at upper rpm's. -30 is way rich, I've never heard of it being that bad. How are the 02 readings? A few people have gone rich with a clogged cat also, that may explain the boost going up.

 

[imported_snoop]

Originally posted by Diavolo@Jul 8 2004, 04:20 PM
My IAC check at idle and cruise?

i dont think that is what IAC means :lolsign: :lol:

 

[imported_Ron Vogel]

Chrys is the guy to ask on this, he had a big richness problem just like this last year. I can't remember what he had to do to fix it. He also had the ICCU, I think he was setting it at like 60% or something to try and fix to no avail.

 

[imported_Diavolo]

my IAC's are at 0.

 

[imported_Diavolo]

I am not running rich. It is only for the moment while the car is shuddering. Elsewise, with the ICCU, I got my LFT's around 0.

My settings are 97% 99% 103%

 

[imported_Diavolo]

I just scanned (2 sec ago) and my o2's drop down to <100 and even hit 0 (this is on acceleration, no decel). So maybe my o2 sensor?

 

[imported_Ron Vogel]

Yeah, kinda sounds like that, but I would make sure you don't have fuel delivery issues too. It may actually studder from being lean, then overcompensates the enrichment. A good sign of a bad 02 sensor is that it's made by Bosch, or the crosscounts are slow.

 

[imported_Diavolo]

so even though my lft's are at 0 at idle and cruise, there could be a problem or running too lean. I will set my ICCU back to 100% and see what happens there.

 

[CoolGTX]

0 IAC= huge vacumm leak.


make sure all your O2 wiring is intact.

Chrys said he took off his A/F gauge, and his car ran 12.3, because that was the problem... <_<


HTH's

 

[superchargedgp]

Originally posted by CoolGTX@Jul 8 2004, 08:03 PM


Chrys said he took off his A/F gauge, and his car ran 12.3, because that was the problem... <_<


HTH's

hehe maybe i should take my gauges off and run 11's :lolsign:

 

[imported_Diavolo]

Well, my cousin was looking at my AC (it wasn't working) and pressed insomething and said I didn't have much pressure in my AC. Said there was probably less than 10 psi when it should be above 100psi. (if that makes sense). It did start after that day.

hmmmmmm.

 

[ThaLord]

My car does the same thing.. my IAC's are fine... no vacuum leak..

My o2's drop so low, it is freaky... no knock.. which is kinda weird... I have changed spark plugs.. o2 sensors, to no avail... I am changing my coil packs, and wires next... even though my car doesn't report misfires... which is strange.. (it seems so much like it is)

Let me know what you come up with.. and I will let you know. as it seems we are fighting the same problem.

John