Car runs like SHIT in idle, part throttle, good under boost

[treckin]

Hey,

Heres the story:
I recently put in 540cc Yellowtop injectors and a 2g MAS, as well as did a fuel pump rewire.
I took the car to Tahoe and back, about 400 miles, and a few weeks ago, I tried to go back up. Well, the car started to run like shit half way there.

It stumbles and gives a 'put put put' backfire, and idles slightly choppy. Under partial throttle, its the same story. It boosts fine and strong, although the car also has a phantom knock issue Im still dealing with.

Im going to swap the injectors back to stock next weekend, as I was thinking it could possibly be a stuck injector.

I have spark, plugs are gaped correctly. Throw's no codes.

Any idea's?

PS: Anyone have any tips on belt squeal? I have adjusted the #### out of the alternator and PS pump belts, but the squeal is horrendous. The belts look good.

 

[Gstclipse69]

I would definitely search for belt sqeal. Sounds like the harmonic dampener.

 

[1sttimedsmr]

well i have the same problem (check your timing in the crank and in the cam gears, i'll bet you they won't match)and it seems that i'm going to have replace the crank pulley and or cas.

 

[blowinsmoke95]

... okay guys i have this same exact problem... car is in PERFECT time... i just aquired the car not too long ago.. the original motor had a knock... then it locked up... i swapped it with another... both before and after the swap ive had this problem... at idle and part throttle the car runs like ass and the uego shows lean off the gauge... but when boost hits, its runs like a raped ape... and afr's go down around 11's or so... ive got a video of cold start and idle with a couple revs... sorry sound quality is the greatest but it has a horrible miss at idle and part throttle..... new plugs NGK BPR6ES, wires, newish o2 sensor, everything is hooked up... MAF got pulled from a perfectly running car and is untampered with... if u need to know anymore then ask.... if it means anything, this was originally a A/T car... 390cc injectors, A/T fuel pressure reg., and TD04


LINK TO VIDEO: http://www.youtube.com/watch?v=99Iy1wR-hX4

 

[91talon27]

When you are saying it runs good under boost. Do you mean at wide open throttle under boost or just anytime it's under boost. If it runs good while under wide open throttle but like crap while idling and at part throttle it could be a bad throttle position sensor.

 

[blowinsmoke95]

when the maf is plugged in... at idle it misfires really bad and the wb shows full lean... and is real sluggish and misfires until boost kicks in, once boost hits tho, the car screams... BUT i can unplug the maf and it will run so goddamn rich at idle you could probably put a can at the end of exhaust and recycle the unburned fuel... but anything over 3/4 throttle it wants to backfire then pulls even harder... im new to the dsm game and this caR will be my daily in the spring/summer/fall months.... i just dont understand it....

 

[91talon27]

It still sounds like the TPS to me.

 

[blowinsmoke95]

okay then... how do i calibrate it??? i tried turning it in different increments and driving it to see if it changed anything and no go... on my probe gt you calibrated the tps by jumping the ground and another terminal in the diag. box then turning it just until the fan kicks on...

 

[91talon27]

This needs to be done while the Throttle Body is out of the car due to the fact the fuel rail blocks the lower screw to adjust it.




Hook up some jumper wires (Alligator clips) to the TPS. The POS+ to the Number 1 terminal and the NEG - to the number 4.

The terminals are: 4, 2 and 1

There is a space for #3 but there is nothing there.

_II__________II___II__

_4___________2___ 1 _




Measuring the resistance, set meter to Ohms.

It should read 5K Ohms. This is the resistance in the closed throttle position.


Now, move the POS + jumper wire to the number 2 terminal. Leave NEG - on number 4.



With the throttle closed it should read .9K Ohms (Changed per Data logger). Pic shows 1.1K Ohms.


Open the throttle all the way open and the meter needle should move while opening and stop at 5K Ohms.


Loosen the two screws (Phillips screwdriver) and rotate it to set the closed resistance to .9K Ohms (Haynes say 1.1 Ohms but Datalogger rebukes that). The pin resistance will remain about the same (5K).

 

[blowinsmoke95]

okay... thanks man... ill deff. try this tonight before it gets too dark... thank you for taking the time to post that for me... ill keep u updated after i try this...

 

[rEclipserGST]

okay... thanks man... ill deff. try this tonight before it gets too dark... thank you for taking the time to post that for me... ill keep u updated after i try this...

Pull the ECU before you do that junk. I replaced a TON of parts trying to fix a "running rich and like shit" issue. Best bet is to examine the ecu and if it hasn't been rebuilt yet, I would have Steve at least test it and maybe rebuild it. My car runs like a champ now that the ECU was rebuilt. Had a blown capacitor. My ECU looked PERFECTLY fine when I checked it 6 months ago before sending it to Steve.

Other than that, maybe your ECU needs to be for an M/T. Do you still have the TCU from the auto in there?

treckin: Did you fix your issue? That is like blind tuning. I've done it, but I would not recommend it. For the belt squeal, check your water pump. Might have a slight wobble or play where the pulley sits on it. My car squealed more and more as the water pump went bad. Replaced it with a brand new one with brand new belts and no squeal.

 

[blowinsmoke95]

UPDATE::: okay guys... i've set the tps... checked/changed plugs, timing, swapped maf, swapped injectors, rails, fpr, all kinds of shit. and i still have the same problems... lean at idle, part throttle,...pretty much anytime its not seeing boost pressure... can i get a link or something to a vac diagram of the fpr??? i think it might be wrong... is the fpr supposed to see vaccum??

 

[Gstclipse69]

http://www.dsmtuners.com/forums/new...c-wire-diagram-emissions.html?highlight=taboo

Yes the fpr does see vacuum.

 

[blowinsmoke95]

okay... so that rules out the fpr suspicion... anyone konw or have an idea to try???? open to all offers... or suggestions...