Proud new SHO owner havein some drivability problems

[Cward]

Well, just got a 93 MTX. It has a few issues. First it has a flat spot during acceleration around 3000-4000 rpm it just falls on it's face during WOT. No CE light nothing. 2 it has a slight stalling problem. It's intermittent though In fact it didn't stall at all today. When it does stall it's when I'm decelerating to stop and the rpms drop to about 400-500 rpms and then jump up to aorund 1200 and then it dies. I put some injector cleaner in it today before a pretty long trip, 90 miles round trip, and it didn't stall it all. Doubt it was the cure though. 3rd problaem is it has a erratic idle when it's cold. Start it up and it'll run fine for 2 minutes and then it starts to move between almost dying(300rpm?) and 1200-1500 rpm. Sometimes it does actually stall. Not always though. Idle seems to even out around 900rpm once she warms up. Once again the CE light isn't on. I haven't checked codes, as I don't know how. Is there a way to do this without a scanner?? I'm kinda leaning towards a TPS for these problems, but I'm new to the SHO platform and need a little help.
Thanks in advance,

 

[Ishodu]

Sounds like it could be a combo of the TPS and maybe a dirty MAF. To check codes check out the link in my sig. You need nothing more than a paper clip.

 

[jaded93atx]

I would also add a dirty or faulty IAC idle air control valvle to the list, it will cause a surging/ bouncing idle when not functioning properly, and acts up when the engine reaches operating temp, it wont always throw a code if its stuck. When you mention that " it falls flat on its face at 3-4000", does it pick up again after 4000, if so then it sounds like the tps(it throws a code) if not then your secondaries may not be opening (they may be stuck or have a vacuum leak)and may be something to check out along with the TPS, its an easy check just rev the engine hard with the hood up and make sure the secondary solenoids on the intake flip open at 4000. Like ISHODU said use his links to check the codes without a scanner and see what if anything is stored. If you actually don't have any codes stored then you need to focus on problems that dont throw a code when they fail.
Hope this helps

 

[bgjohnson]

I would also add a dirty or faulty IAC idle air control valvle to the list, it will cause a surging/ bouncing idle when not functioning properly, and acts up when the engine reaches operating temp, it wont always throw a code if its stuck. When you mention that " it falls flat on its face at 3-4000", does it pick up again after 4000, if so then it sounds like the tps(it throws a code) if not then your secondaries may not be opening (they may be stuck or have a vacuum leak)and may be something to check out along with the TPS, its an easy check just rev the engine hard with the hood up and make sure the secondary solenoids on the intake flip open at 4000. Like ISHODU said use his links to check the codes without a scanner and see what if anything is stored. If you actually don't have any codes stored then you need to focus on problems that dont throw a code when they fail.
Hope this helps

couldn't have said it better myself.

 

[Cward]

Well, it warmed up a little today (21), so I got to look at the SHO a little. The secondaries are opening, the two little vac solenoids(one front,one rear) on the intake are flipping open. The power doesn't seem to come back now though after 4000. Well I can put the pedal to the floor in 1st, 2nd, and sometines 3rd with no problems. But 4th and 5th if I go past 3/4 throttle it bogs really bad. Like it's either starving for fuel or maybe not getting enough fuel?? Could the TPS still be the culprit. Is the TPS SHO specific? Do I have to have the part number to get the correct one? Now is there a special cleaner to clean out the MAF? Anyone have one in particular they like? Is the IAC on the throttle body like the TPS? Can the IAC be cleaned?? I'm going to try to check for codes today or tomorrow. If it stays warm enough.

 

[Cward]

Alright checked the codes, Key on/ Engine off got 114, 539, 556. Now will the IAT being out of range cause any off my problems?? On 539 the defroster was on which cycles the compressor. On 556 I'm stumped, I don't seem to be haveing a fuel pump problem. Stored codes I got were 172, 173, 177, 211, 542, 556. 3 O2 codes, an ignition signal code, 2 fuel pump codes. Now stored codes are just something the computer picks up at sometime. How long are they normally stored for?
Key on/Engine on I got 116, 114, 538. I don't think 116 is causing any of my problems, coolant sensor out of range. Should I replace the sensor though? Not sure if 114 is causing anything. Got that could with the engine off too. Got 538 because I forgot to goose the throttle. Trying to read how to check the codes while checking them,LOL.
Also ran a cylinder balance check and got a 9 so no problems there.
Well, what do you guys think? Solenoids for secondaries are opening, everything else seems to be in order for the most part. Should I stick with the TPS, IAC valve, and MAF checking out/cleaning? Is there something else you guys can think of?
Thanks!!

 

[wood_e]

You should first reset the computer to see if any codes come back. If they do then replace some stuff.

If your O2s are original I would change both (Bosch PN 15716)

Your ECT is easy to change and really effects driveability. Buy the metal sensor (Wells PN SU201)

The 211 code is tripped by either the crank or cam sensor. I want to say cam sensor... you should replace that

Your IAT code was probably from the weather being below 40 degrees outside... I would know

 

[Cward]

Not sure if the O2's are original or not. Probably are. It's the same sensor front and rear? Would the ECT cause a stalling, idle problem? I don't think any of those codes are causing my WOT problem though.

 

[Cward]

Okay, I reset the computer and ran a few short errands. Ran codes again when I got home. Key on engine off 114, 556. Not worried about 114 it's 21 degrees outside. 556 kinda makes me worried, fuel pump relay primary circuit fault. Now stored codes 542,543,556 all 3 fuel pump codes. 542 shows to be fuel pump open, bad ground or always on. HMMMM 543 fuel pump monitor curcuit shows no power. Service 556 first if present. Well I got that twice so far. Okay now key on engine on 114,411,538,536. Ah ha! 411 makes sense! Idle being goofy and all could this be the IAC? Last two I'm not too worried about 538 I forgot to goose the throttle again. 536 Brake on off open or shorted to ground, well the damn car stalled just as the key on engine running codes started. So I'm figureing that caused the brake code. Car still falls on it's face at WOT.
So should I clean the AIC and then replace the TPS? Any other suggestions now??

 

[Cward]

come on guys. No suggestions?

 

[AutoSHO]

A few steps I would take:

Clean the MAF
Replace the TPS and ECT. Both affect driveability, idle, mixture, and timing advance.
Check the plug wells for oil

 

[wood_e]

A few steps I would take:

Clean the MAF
Replace the TPS and ECT. Both affect driveability, idle, mixture, and timing advance.
Check the plug wells for oil

To add to this I would clean your IAC and or get a new one

 

[Cward]

Thanks guys. That's were I'm gonna start. I'm gonna change the o2 sensors too.