Scanmaster Reading

[Eric Stage I]

Sent you an email. I'm starting to question the injectors now, since that's when the problems started. I'm sending you another set.

 

[bmackinnon]

Sent you an email. I'm starting to question the injectors now, since that's when the problems started. I'm sending you another set.

TO GUAM!! not to hijack the thread (which I'm following, but unable to offer any great ideas), but hat's off to Eric!!... a superb example of premium customer service!! I said it before... I will DEFINITELY be contacting you soon for a 60's/chip combo.... I'm savin' my pennies...

 

[Colas_011]

Still having problems with engine choking when I hit the throttle. Here are some of the things I've done/changed since my last post.
1. replaced inj/chip from Eric.
2. checked all hoses & lines again.
3. disconnected cam sensor with engine running...no change.
4. replaced O2 sensor (GM)...no change.
5. replaced plugs & wires again...no change.
6. replaced ignition module & coilpack (GM)...no change.
Current Scanmaster readings...AF 06-07, L8 46, bAt 13.7, Int 137, bL 131, CLt159, AtS 85, r 800, tPS .42, IAC 35, cc 12-254. Note: before I change my ign module & coil pack, my AF was 04-06.
I'm not sure if this would make a difference, but, I had my throttle body & plenum worked. and the throttle shaft has what I think to be a little too much side to side play.
The only thing that I think is left is the computer. I really need some help please. Thanks Nick Eustaquio.

 

[TurboBuRick]

Try unplugging the MAF and see how it runs.

 

[melrob94]

Fuel filter and/or pump maybe.

 

[Colas_011]

The following items have been replaced:
New gas tank, reds f/p, fuel filter, LT1 MAF/Translator, Adj fuel press reg, frt mount ic, cold air, reworked tb & plenum...steve monroe, coil pack & ign module GM, O2 sensor, 42# inj/91 tt chip, hotwire, f/p gage, TH downpipe, new adj boost act, pcv GM, TPS, This is all I can remember for now. One thing I just noticed...when I hit the throttle...the fuel press drops, when I let off the throttle fuel press goes right back up to 38-40 psi. Additionally, this only happens when the engine is warmed-up. Thanks Nick Eustaquio.

 

[bmackinnon]

One thing I just noticed...when I hit the throttle...the fuel press drops, when I let off the throttle fuel press goes right back up to 38-40 psi. Additionally, this only happens when the engine is warmed-up.

Well, there's your problem.... It should do the exact opposite.... when you 'stab' the gas, the vacuum jumps DOWN, which should cause the fuel pressure to jump UP... and continue to rise as you transition into boost... and it should rise EXACTLY 1 psi per pound of boost... so.... adjust your BASE fuel pressure (0 boost, 0 vac, vac. line off the fpr) to 43 psi. Now go for a drive an closely watch the fp gage... your OPERATING FP should equal your BASE FP + BOOST PSI.... so if you run 18 psi boost, then your wot FP should be 43 + 18 = 61 psi. If this isn't happening, then the problem lies in either the vac/boost supply to the FPR, the FPR itself, or the fuel pump (most likely). You will notice the fuel pressure will drop from the base setting when you re-attach the vac hose to the fpr while idling.... this is because the engine is under vacuum at that point, which will drop the FP...

You are getting a LEAN spike/stumble, and if the above conditions aren't met, your headgaskets are going to be the next problem....

 

[Colas_011]

Under gradual acceleration...fuel pressure does increase and increase with boost. When I hit the throttle as in a sudden burst...engine just stumbles. This is also the second fuel pump I installed...zero mileage on the first one. Thanks Nick Eustaquio

 

[Colas_011]

Just replaced the coolant temp sensor...shutgun...no change. Verified fuel pump press...press does in fact increase when I hit the throttle...only 2 psi no load. Sprayed some silicon fluid on the throttle shaft in hopes it may swell up the seal due do shaft side to side play...still the same. Thanks Nick Eustaquio.

 

[Colas_011]

Forgot to mention...unplugging the MAF caused the engine to shutdown. Thanks Nick Eustaquio

 

[BoostedEvIL]

You probably did this already, but did you check for vacuum leaks? On your fuel gauge, does the needle move pretty smoothly, or does it dance around any more than your used to? Also how long does the car hold it fuel pressure after you shut it off?

 

[Colas_011]

First, I want to thank everyone, especially Eric Marshall for helping me out with my parts issues. He went out of his way to get me the MAF & Translator and ship it to me here in Guam. "CLASS ACT" Well as everyone has seen on my post...a lot of parts have been changed and I finally found the culprit. My new TPS (GM) went south. When I initially installed it, the readings were at .42 & 4.7 wot. I decided this evening to go back and check everything again...TPS stayed at .42 wot. Fortunately, I had another new TPS...installed it and made my adjustments. Engine now accelerates without stumbling. What a sigh of relief!!!! Thanks for all the help & inputs. I couldn't have done without you folks. Thanks Again!!! Nick Eustaquio

 

[fastlikeanascar]

You probably did this already, but did you check for vacuum leaks? On your fuel gauge, does the needle move pretty smoothly, or does it dance around any more than your used to? Also how long does the car hold it fuel pressure after you shut it off?

hijacking well not so much since he fixed his car.. but what does this mean if your gauge is doing this & if it doesnt hold pressure to long.

 

[87TTypewriter]

what a hassle. my buddy had the same thing happen to him on his LS1 car. A bad TPS can turn into an expensive guessing game. did the same thing on my lt1 car. couldnt figure out wtf was wrong with it for a long time and allot of $$ in guessing game. turned out to be burned wires throught the heat sleeves that i had replaced twice and then over looked once i tucked them away and wrapped them. by chance i pulled the sleeve down and the rest is history. Im glad you got your car fixed man.

 

[bmackinnon]

A bad TPS can turn into an expensive guessing game.

No guessing involved if you have a scan tool.....

Glad you found the problem Nick! Prop's, Eric!! (TurboTweak)!!

 

[Fenderbender]

Hello, I've just installed a few items on my 87GN. TT chip & 42# inj, frnt mt intercooler, cold air intake, reworked tb & plenum, new tps. Engine stumbles pretty bad while trying to accel in park. Thanks in advance for any assistance. Here are my SM readings: mv 394 AF09 L8 43 bAt 13.9 Int 128 bL 122 MPH 00 CLt 146 AtS 88 r 775-850 (bounces) tPS .42 IAC 10 cc 09-233 (bounces all over). Thanks again!!! Nick Eustaquio

Nick can you help me work on my car sometime, you really seem like you know what your doing!