Frustrated

[SHOYAY]

92 mtx 174k miles (10k on rebuilt engine, catless y-pipe).... I'm at the point where I'm a little frustrated and have to walk away from it for a while.... Problem: when I go to accelerate, the car falls on it's face and nearly stalls unless I let off the throttle...if I slowly gain speed and then get on it when it's moving good, it then accelerates better but not great. At an idle if I step on it and rev it up, falls on it's face for a second and then revs up and once the rpms are up, it revs good. Also if I just let it idle it'll start surging and stall and be hard to restart unless my foot is partly on the gas pedal pushing down about an inch.
No codes, good fuel pressure....
I've exchanged good used parts from my donor car(94 mtx)....tps, iac,maf and have gone over as many vacuum lines I can find....what am I missing or forgetting that I should look into?! Any opinions are very much appreciated!

 

[KyngofPop]

92 mtx 174k miles (10k on rebuilt engine, catless y-pipe).... I'm at the point where I'm a little frustrated and have to walk away from it for a while.... Problem: when I go to accelerate, the car falls on it's face and nearly stalls unless I let off the throttle...if I slowly gain speed and then get on it when it's moving good, it then accelerates better but not great. At an idle if I step on it and rev it up, falls on it's face for a second and then revs up and once the rpms are up, it revs good. Also if I just let it idle it'll start surging and stall and be hard to restart unless my foot is partly on the gas pedal pushing down about an inch.
No codes, good fuel pressure....
I've exchanged good used parts from my donor car(94 mtx)....tps, iac,maf and have gone over as many vacuum lines I can find....what am I missing or forgetting that I should look into?! Any opinions are very much appreciated!

Anytime I’ve encountered this I was having a fuel delivery/starvation issue or the timing was off after a timing belt change. I know EXACTLY what you’re talking about and have experience it countless times in my previous SHO’s. Does it make a pop sound in the intake when trying to get up to speed, almost like a backfire thru the intake??

 

[SHOYAY]

I haven't noticed that on acceleration cause I pretty much have accelerate so slow. I did notice that tho a couple times when under the hood revving it up manually.

 

[SHOYAY]

Anytime I’ve encountered this I was having a fuel delivery/starvation issue or the timing was off after a timing belt change. I know EXACTLY what you’re talking about and have experience it countless times in my previous SHO’s. Does it make a pop sound in the intake when trying to get up to speed, almost like a backfire thru the intake??

I haven't noticed that on acceleration cause I pretty much have accelerate so slow. I did notice that tho a couple times when under the hood revving it up manually.

 

[sperold]

Was there an event that took place, after which the car started acting like this?

You have done all the right things in experimenting with parts.

Make sure your Spout connector is in place, as that affects your timing advancement (locked at 10 degrees).

Get someone else to operate the gas pedal from inside the car and go through the sequence while you lift and move the wiring to your Idle Air Control and Throttle Position Sensor.

You should have codes if your Intake Air Temperature sensor is acting up, and really there should be codes for all these things that have been mentioned. Maybe try the paper clip method if you have used an OBD1 scanner.

It does not happen to be a California swapped engine with that exhaust bypass thing hanging off the back of the intake? But again, I think that triggers a code, but only if the car came originally with it. Long shot, but look anyways.

The oxygen sensors always throw a code, so they are probably OK.

 

[SHOYAY]

Was there an event that took place, after which the car started acting like this?

You have done all the right things in experimenting with parts.

Make sure your Spout connector is in place, as that affects your timing advancement (locked at 10 degrees).

Get someone else to operate the gas pedal from inside the car and go through the sequence while you lift and move the wiring to your Idle Air Control and Throttle Position Sensor.

You should have codes if your Intake Air Temperature sensor is acting up, and really there should be codes for all these things that have been mentioned. Maybe try the paper clip method if you have used an OBD1 scanner.

It does not happen to be a California swapped engine with that exhaust bypass thing hanging off the back of the intake? But again, I think that triggers a code, but only if the car came originally with it (which it did not). Long shot, but look anyways.

The oxygen sensors always throw a code, so they are probably OK.

There was no incident that caused this to have happened
No help to run the gas while I check wiring, that I'd have to do on my own.
Didn't think of spout connector... one to check thank you.
It is an original California car when it was new.

 

[zoomlater]

There was no incident that caused this to have happened
No help to run the gas while I check wiring, that I'd have to do on my own.
Didn't think of spout connector... one to check thank you.
It is an original California car when it was new.

Can you pull on the throttle cable and jiggle the wires when the car in neutral and wheels blocked
Can't remember if 92 MTX's had EGR on the CA cars, but usually you had really bad gas mileage and it would throw a code. When my 94 ATX had a bad DPFE sensor/clogged lines, the car would stumble when you tried to accelerate

 

[BaySHO Performance]

I've had this exact same problem with a dirty MAF, but you say you've already tried a replacement. With no codes and no perceived vacuum leaks and plenty of fuel, I'd go after a bad plug or wire. And make sure none of the intake couplers are cracked.

 

[SHOYAY]

Well, got some codes using paperclip and not the obd1 reader
KOEO= 542
KOER= 116
172
136
332
538

 

[BaySHO Performance]

542 Fuel pump secondary circuit failure can probably be ignored. Gets generated if the car stalls at a light.
116, ECT: car was probably not fully warmed up.
172, O2 sensor not switching, indicates lean. O2 Sensors: Bosch (2 MTX) 13942 $87 Autozone
132 bad O2 sensor again

332, insufficient EGR flow: take the small hose off the back of the EGR valve. Attach a hose of the same diameter to the valve port and suck on it. You should hear the valve moving back and forth, indicating a good valve. Now start the engine and suck on the hose again: the engine revs should drop. If not, the nostrils in the intake behind the throttle body are blocked. Remove the TB and clean them out.

538 operator error, nothing wrong with car.

None of the codes should have the car run rough except possibly the O2 sensors, so try replacing them.

 

[SHOYAY]

542 Fuel pump secondary circuit failure can probably be ignored. Gets generated if the car stalls at a light.
116, ECT: car was probably not fully warmed up.
172, O2 sensor not switching, indicates lean. O2 Sensors: Bosch (2 MTX) 13942 $87 Autozone
132 bad O2 sensor again

332, insufficient EGR flow: take the small hose off the back of the EGR valve. Attach a hose of the same diameter to the valve port and suck on it. You should hear the valve moving back and forth, indicating a good valve. Now start the engine and suck on the hose again: the engine revs should drop. If not, the nostrils in the intake behind the throttle body are blocked. Remove the TB and clean them out.

538 operator error, nothing wrong with car.

None of the codes should have the car run rough except possibly the O2 sensors, so try replacing them.

Wasn't fully warmed up.
Car stalls all the time after it surges during idle especially cold after idle comes down, idles good when warmed up, but will then surge and stall after I rev it and let off
There is no egr

 

[BaySHO Performance]

This was originally a California car with EGR. If it now doesn't have one, it must have a 49 state intake or the place where the EGR valve attaches to the intake must have been blanked off. Also, the rear exhaust manifold wopuld have a similar issue.

I'd go after the O2 sensors as a first step.

 

[SHOYAY]

Has 49 state intake and catless y-pipe

 

[BaySHO Performance]

The rear exhaust manifold has an opening where the EGR tube attaches. That also must have been swapped out for a 49 state one, or the orifice blanked off.

 

[SHOYAY]

And what is this thing? It's just laying on top of transmission.

 

[SHOYAY]

The rear exhaust manifold has an opening where the EGR tube attaches. That also must have been swapped out for a 49 state one, or the orifice blanked off.

Must've, exhaust isn't leaking near the manifold anywhere

 

[SHOYAY]

When on a test drive, cruising at 55 and cel came on and now have a new code stored 556.

 

[BaySHO Performance]

Fuel Pump Primary Circuit Failure. You also had an FP2. Might be worth a try to get a new M code CCRM:

http://www.shosource.com/catalog/product_info.php?cPath=61_46&products_id=793

But replace the O2s first.

 

[SHOYAY]

Fuel Pump Primary Circuit Failure. You also had an FP2. Might be worth a try to get a new M code CCRM:

http://www.shosource.com/catalog/product_info.php?cPath=61_46&products_id=793

But replace the O2s first.

M code? I'll have to see what's in it now.
O2s aren't that old

 

[BaySHO Performance]

You should see a large red M on the CCRM (or IRCM as it was called in the Gen1 days). If the O2s are fairly new, go after the wiring.