Ideas on why it's stumbling?

[GRAYGHOST]

Idles good, runs good under normal acceleration.

When I start to get in it hard just as boost starts to come on, it gives a stumble a couple of times, then it will go full tilt and smooth out.

Seems like it is right around 4K rpms....and just when the boost is starting to come on, like between 1-5 pounds......

I have new 85mm maf, 72's, trans +.....direct scan numbers seem good to me....although I did notice that TPS readings on a wot run where a little low, 4.3....however when I checked it with car off, ign. on, I was getting .44 key, then 4.6-7 wot.

Why would it show this with ign on, then when running it does not show the same readings???? Could this be the stumble?

Any ideas appreciated.....I've played with translator a little, went to rich idle, turned timing up, down, reset TPS...

 

[Warp6]

Mike, is your second pump coming in around the time of the stumble?
How does the fuel pressure look? Not too high is it?

 

[GRAYGHOST]

feul pressure is dead on .45 static, using the extender extreme...

I was trying again last night to figure it out, and now I don't think my 2nd pump light is working, I turned the set screw on the hobs switch damn near all the way out, no light, still stumbled. then I turned it close to all the way in, no light, stumble...I think I might disconnect the wire all together to eliminate the 2nd pump all together.

Somone else had mentioned a vac leak. Does this make sense?

 

[GRAYGHOST]

so I'm the only one who has ever experienced this before, huh?..................bump!

 

[Sleeper-6]

Not too sure on the stumble, Cam Sensor adjustment? I had a similer prob but it went away as soon as I tossed the old MAF went to my new Trans+ setup.

As for the TPS, are you sure the floormat haden't moved under the pedal while you were driving?

 

[Warp6]

Originally posted by GRAYGHOST
so I'm the only one who has ever experienced this before, huh?..................bump!

Mike, I'd like to see the DS file

 

[Lee Thompson]

pump

Are you using a hobbs switch to bring your second pump on? If so, turn key on without starting eng. use a short jumper wire to jump across the hobbs switch. Should be able to hear if pump is running. You probably already knew this. Just a thought.

 

[JoeNational]

Well i experience a similar or the same prob but only when iam on the highway and iam already cruising at lets say 60 i try to get on it and the whole car seems to be going over bumps and i get nothing out of the motor , i spoke with ron from rons customs and had my coil pack changed but still have the problem but not all the time so maybe you should check out your coil pack and get a high performance one cause thats what iam looking into.

 

[NC87GN]

If the TPS appeared low I would blame that on the infamous floor matt being in the way. Achieving 4.5V + at WOT is not a critical number you must achieve.
As far as the stumble goes, IMO I would inspect all your plugs and their gap. If your running 28# gap those plugs to .028-.030" with Autolite 23's. Ohm out the plug wires. Look at DS and monitor voltage, BLM's, IAC's in text mode when the car stumbles. When it stumbles is it in PE mode? Also verify if the car is in open or closed loop (maybe 02 sensor related if in closed loop?)
Some things to consider first before swapping ignition modules, MAF's, coil packs etc...
Oh yea 1 more thing, leave the FP at 45 psi! Change the box to account for a rich or lean idle.

Mike Banas
87GN

 

[Warp6]

Originally posted by NC87GN
If the TPS appeared low I would blame that on the infamous floor matt being in the way. Achieving 4.5V + at WOT is not a critical number you must achieve.
As far as the stumble goes, IMO I would inspect all your plugs and their gap. If your running 28# gap those plugs to .028-.030" with Autolite 23's. Ohm out the plug wires. Look at DS and monitor voltage, BLM's, IAC's in text mode when the car stumbles. When it stumbles is it in PE mode? Also verify if the car is in open or closed loop (maybe 02 sensor related if in closed loop?)
Some things to consider first before swapping ignition modules, MAF's, coil packs etc...
Oh yea 1 more thing, leave the FP at 45 psi! Change the box to account for a rich or lean idle.

Mike Banas
87GN

ha! Banas, you might want to put that in English for him!!

 

[GRAYGHOST]

Brand new autolights gapped at .030, fuel pressure is .45 line off, played with rich idle, lean idle, no differences.

Floor mat is NOT under the pedal, when it stumbles it seems to be before it hits PE mode.

Voltage does not seem to be an issue with the Reds booster.....

Translator is set for open loop, (110 octane)

Anybody have experience with the 85mm MAF? It is a brand new SLP performance on it.

 

[GRAYGHOST]

Well I geuss I must not be the only one stumped on this stumble.........