SHO is slow, part 2 *Updated*

[AutoSHO]

Update:

I cannot figure the thing out. Its got a couple new symptoms, too. If I let it idle while sitting still for more than 30 seconds, it dies. Just sputters all the sudden, and dies. Usually 30 secs-1 min after letting it drop to idle.

Also, I noticed something with the power loss: With the MAF unplugged, it picks up some power at this magical changeover point, the same point at which it loses power with the MAF plugged in. the TPS is new, and it does this regardless of TPS (new or old). I am at my wits end. I tried the following:

Unplug Oxygen Sensors - No change
Unplug Intake Temp Sender - No Change
Unplug MAP/BARO sensor - No Change
Unplug MAF sensor - Runs better WOT, but not as well low throttle opening. Dies after idling.

Original Post:

Well, I thought I had the problem cornered. With the MAF unplugged, my car runs much better. With the MAF plugged in, at about 50% or more throttle, the car falls flat on its face (lean) but below 50% throttle runs great.

I figured it was the MAF, and replacing it would solve the problem... right? Wrong.

I am now so bewildered I do not know what to do. Here are the symptoms I have noted so far:

With the MAF unplugged:
- Runs good rolling onto the throttle to WOT
- Hesitates, occasionally pops out the intake if I "goose" the throttle at low rpms. Hesistates, and doesn't really gain rpms.
- Not too much low end power. Probably because the computer cannot calculate the load based airflow.

With the MAF plugged in:
- Runs much better at low rpms. Not nearly as much hesitation, no pops, etc.
- At anything above ~50% throttle, the car feels like it loses about 30-50 ft. Ibs of torque. Very definite power loss.
- Exhaust note once it goes into low power area is much buzzier.

With MAF plugged in, and TPS unplugged:
- Very, very small throttle openings it registers. Anything larger than about 3% and it does not run at all. If I snap the throttle open the car bogs down (this is no load, sitting still in the driveway) and if I let off it will idle down.

I am literally at my wits (and wallet's) end. I have new plugs and wires on the way, but I seriously doubt they have anything to do with it, since it seems to run so differently with the MAF plugged in or unplugged.

Replaced: IAB, MAF, TPS
Fuel Pressure in spec.
60K was done on time.
Codes: None
Headache: Like a dive off the roof.

<small>[ May 02, 2003, 08:49 PM: Message edited by: AutoSHO ]</small>

 

[twr]

Chris,

You don't have an LPM do you?? Sounds like how my car used to run with the first program I got from Ted.

 

[AutoSHO]

twrsho:
Chris,

You don't have an LPM do you?? Sounds like how my car used to run with the first program I got from Ted.

No LPM, never had one. The seal is still on the computer. The car has been doing this since I got it. I can't believe it will run fine without the MAF, but with a brand new one, it runs poorly.

 

[SolidState]

What does the ACT sensor do again?

(not being a smart *** ....I though that it sensed the density of the air entering the MAF)

 

[AutoSHO]

SolidState:
What does the ACT sensor do again?

(not being a smart *** ....I though that it sensed the density of the air entering the MAF)

ACT = Air Charge Temperature

Its basically a glorified thermometer, but instead of moving the mercury it changes resistance based on temperature.

 

[AutoSHO]

If it still exists, stay as far away as possible from "I'll SHO-U-Performance" in Westminster, Colorado. I've got a receipt from the previous owner for a 60K.

Well, in the never ending hunt for a problem with the SHO, I decided
to pull the intake to check a few electrical connections, and clean
out the manifold. What I found absolutely awed me. They supposedly
did a full 60K including Valve lash.

First thing: Front 3 spark plugs weren't tight. By not tight, I mean
I didn't need a ratchet to remove them.

Second (and very displeasing) thing: The rear valve cover has never
been removed. Ever. This means that not only are my plug wells full
of oil, but only 1/2 the valve lash adjustment was ever completed.
Now I know what that noise is for certain.

I am in awe. If they are still in business, don't go there. You're better off without a 60K. The manifold didn't get cleaned, 1/2 the valve lash was not done, and the back valve cover leaks like crazy. 60K Indeed.

 

[SHOSIG]

The guy who used to run I'll SHO U now has a shop called Pro Street Performance in Westminster(Brent). I would call them and let them know what you discovered.
Anyway, this is a long shot...on my SHO where the wiring harness plugs into the ECU, I had a vacuum hose that rested on the wiring and over time had rubbed away the insulation and almost broke 4 wires...one of them was for the CID sensor. I fixed the wires and the car ran much better!

 

[AutoSHO]

SHOSIG:
The guy who used to run I'll SHO U now has a shop called Pro Street Performance in Westminster(Brent). I would call them and let them know what you discovered.
Anyway, this is a long shot...on my SHO where the wiring harness plugs into the ECU, I had a vacuum hose that rested on the wiring and over time had rubbed away the insulation and almost broke 4 wires...one of them was for the CID sensor. I fixed the wires and the car ran much better!

Thanks for the info. I might give them a call, I doubt they'll take me seriously or anything, but I figure I might as well let them know their business practices are a bit unorthodox. Charging someone, and then only doing half the work and all.

It should be noted that the guy I bought the car from didn't own any hand tools, and took the car to a service center for anything it needed. This is why I am convinced it is I'll SHO U that was at fault.

 

[SHOSIG]

Let me know if you want the phone number. Brent seems like an alright guy not to pull a stunt like that. He's helped me on some shims that were needed.

 

[AutoSHO]

SHOSIG:
Let me know if you want the phone number. Brent seems like an alright guy not to pull a stunt like that. He's helped me on some shims that were needed.

If you could PM me or email me at [email protected] that would be great. Thanks!

 

[Mike Kopstain]

This is another long shot, but in theory, I think it works... at least in my feable mind.

With the MAF unplugged, your computer goes into limp mode, basically running on a set program that it knows will keep the motor running, but far from optimal. As such, it may not be advancing spark or adding as much fuel as it would if it were running in the regular mode.

With the MAF in, the computer does this, and the plugs/ wires can't keep up.

I guess I'm saying I don't think your MAF is bad, but that the whole problem sits covered in oil in your right bank.

I guess we'll know in a couple days.

<small>[ May 02, 2003, 12:46 AM: Message edited by: Mikeys_Taurus ]</small>

 

[Catastrophe]

What about the oxygen sensors?? Could they be responsible?? My car acted like that, and I had mine changed. Ran fine...

 

[Don89SHO]

Wouldn't running the codes reveal your problem?

 

[AutoSHO]

Don89SHO:
Wouldn't running the codes reveal your problem?

AutoSHO:
Codes: None

It never flashes the CE light either...

 

[AutoSHO]

Clitaurus:
What about the oxygen sensors?? Could they be responsible?? My car acted like that, and I had mine changed. Ran fine...

If cleaning out the plug wells doesn't fix it those are next on the list.

 

[AutoSHO]

See first post for new info (bump).

 

[AutoSHO]

SHOSIG:
The guy who used to run I'll SHO U now has a shop called Pro Street Performance in Westminster(Brent). I would call them and let them know what you discovered.
Anyway, this is a long shot...on my SHO where the wiring harness plugs into the ECU, I had a vacuum hose that rested on the wiring and over time had rubbed away the insulation and almost broke 4 wires...one of them was for the CID sensor. I fixed the wires and the car ran much better!

Thank you VERY much for pointing me in this direction. I found 4 wires to be charfed to the point of showing copper, and I think one is the ground for the MAF sensor. I'm going to fix them once I regain some energy. Working on a SHO all day without showing any signs of improvement makes for a difficult time.

 

[AutoSHO]

AutoSHO:

SHOSIG:
The guy who used to run I'll SHO U now has a shop called Pro Street Performance in Westminster(Brent). I would call them and let them know what you discovered.
Anyway, this is a long shot...on my SHO where the wiring harness plugs into the ECU, I had a vacuum hose that rested on the wiring and over time had rubbed away the insulation and almost broke 4 wires...one of them was for the CID sensor. I fixed the wires and the car ran much better!

Thank you VERY much for pointing me in this direction. I found 4 wires to be charfed to the point of showing copper, and I think one is the ground for the MAF sensor. I'm going to fix them once I regain some energy. Working on a SHO all day without showing any signs of improvement makes for a difficult time.

Well, fixing the wires made a slight difference. However, the problem is still there. Any suggestions would be great!!

 

[SHOSIG]

How did you "fix" those wires? Should have used a soldering iron. Mine were worn very thin on the cam sensor wire and make sure the wires are insulated from each other. Boy, it sounds like a real pain in the a$$! headbang You may need to replace your CID sensor in case it may have gone bad from the wires arcing over from each other. I'm sure you reset the computer. Good luck!

 

[89 black SHO mtx]

i noticed you said that there were no codes stored. does it show you codes if you create one??? like when you unplug the MAF? if not it could be a bad ecm. with the wires uncovered and IF they arced it should have thrown a code. just another shot in the dark here but after reading all the posts it sounds like an ecm problem. not that it is so if the plugs/wires don't help try inducing a code and see if it shows.