1992 sho mtx, performance loss and other issues

[RookieSHO]

I have been experience weird performance loss issues on my car, sometimes it goes crappy making the engine light to come on then sometimes it performed like it should making the engine light to go off, I'll explain the issues in a list to make it easier to understand

Issues

• on a cold start the engine revs up around 2,000rpm then goes down 500rpm acting like it's going to die, sometimes it dies around 1-3 times
• the secondaries doesn't engage until at 4,500rpm (Idk if that's normal or not)
• sometimes I feel the engine pulsing when I try to accelerate
• sometimes while driving the car kinda accelerates slow even if I go to full throttle
  

Parts that I replaced/swapped/cleaned one at a time to see if it fixes the issues

• O2 Sensors (replaced, no affect)
• Vacuum solenoid and vac hoses for the secondaries (replaced, no affect)
  
• fuel pressure regulator (replaced, no affect)
• fuel Pressure damper (replaced, no affect)
  
• Idle Air control (swapped, no affect)
• DIS module (swapped, no affect)
• Camshaft Position Sensor (swapped, no affect)
• Air Change Temp sensor (replaced, no affect)
• MAP Sensor (it went bad in the past so I replaced it with a BWD brand, EC1607 from advance auto)
• TPS (replaced, no affect)
• fuel filter (replaced, didn't make much of a difference)
• Air Filter (replaced, no affect)
• MAF sensor (it went bad about the same time as the MAP sensor so I replace it with a good spare part)
• cleaned the throttle body (had a lot of carbon build up in the inside, actually had to take it apart to clean it better)
• replace the original spark plugs with Autolight Iridium and the wires (fixed part of the problem, feels better than before and don't have to rev as much to go to 1st gear)
• replace the original clutch cable (broke when I was driving while back)

Parts that I haven't tested yet because I don't have the right tools I think

• Fuel Pressure/pump
• fuel injectors

When I drive my car with the engine light on I discover if I turn off the engine then turn it on for a second to get the pump going then start it, the power gets somewhat restored and the engine light doesn't come back on for a while, I don't know what else to look for that might be causing the issues​

 

[Irish Pride]

I would try replacing the PCM with a known good one. I had similar issues in my 89 when I first bought it. Swapped in a different PCM and 6 years later still running strong.

What I did to determine that was the problem, I lowered my glove box so that I could easily access the PCM. When it would start to act up I would reach up and start tapping on the PCM and it would almost always start to run right again.

 

[RookieSHO]

okay thanks for the tip/info and your experience, I just realize I got a 511 code (doesn't always show up on my scanner though when I do multi-tests) when I did the KOER test on my car with a snap-on code reader so it's starting to add up, I'm going to try your suggestion and get me another pcm from shosource.com since that's the only place I can get it when I have the money

 

[sperold]

A failing Crank Position Sensor will give you erratic behavior before it fails entirely. At that point it wont start at all. There is a specific gap that needs to be observed, but with all the work needed to uncover that situation, people change the sensor while they are in there. Sometimes they get greasy, oily, or wet; and that can start the problem.

 

[RookieSHO]

A failing Crank Position Sensor will give you erratic behavior before it fails entirely. At that point it wont start at all. There is a specific gap that needs to be observed, but with all the work needed to uncover that situation, people change the sensor while they are in there. Sometimes they get greasy, oily, or wet; and that can start the problem.

I'm planning on replacing the cam sensor when I replace the water pump and the thermostat

can a bad cam sensor cause the car run hotter than normal but not overheat even if it's idling?

 

[Irish Pride]

can a bad cam sensor cause the car run hotter than normal but not overheat even if it's idling?

No.

 

[luigisho]

The main things to look at are faults in the cooling system. Fans (and/or ccrm relay failure), hoses, tstat, radiator, rad cap, head gasket, temp sensor fail, water pump, gauge failure if temp is ok but reads wrong etc...

 

[RookieSHO]

No.

okay, I actually need to get new spark plug wires again or at least get it replaced or try to fix it, I tried pulling the boot out gently so I can test the resistance/connection with a multi-meter and it fell apart

The main things to look at are faults in the cooling system. Fans (and/or ccrm relay failure), hoses, tstat, radiator, rad cap, head gasket, temp sensor fail, water pump, gauge failure if temp is ok but reads wrong etc...

thanks for the tip

I tested the temp on my car with a temp gun and I pointed at the most hottest spot where the sensor is was at and the highest temp was 216F then I noticed the fans tuned on to dropped it to around 173F, also I checked the dash gauges and it seems to be accurate, I added more coolant and it seem to help it

 

[rubydist]

The code readers don't always read codes correctly from obd1 computers, so I always recommend the manual method of counting flashes on the cel to read codes. Please do that and let us know all of the codes that are stored. The reason I say that is these cars are now old enough that they often have multiple issues at the same time, which makes diagnosis via internet more challenging.

 

[luigisho]

The code readers don't always read codes correctly from obd1 computers, so I always recommend the manual method of counting flashes on the cel to read codes. Please do that and let us know all of the codes that are stored.

1000%.

Second point also.

rubydist for the win

 

[RookieSHO]

The code readers don't always read codes correctly from obd1 computers, so I always recommend the manual method of counting flashes on the cel to read codes. Please do that and let us know all of the codes that are stored. The reason I say that is these cars are now old enough that they often have multiple issues at the same time, which makes diagnosis via internet more challenging.

that's good to know, I'll try that when I get the chance, it's been raining on and off all week

 

[RookieSHO]

I got the codes on my cel test. it's 412, 172, 136, 411, 225

also here is my video for my cel test

 

[rubydist]

please also pull the key on engine off codes - those are the stored codes and are often way more valuable.

412 = idle speed not controlling properly, usually due to a sticking iac but could be vacuum leaks too
172 = lean on right bank, either bad oxy sensor or a vacuum leak
136 = lean on left bank, either bad oxy sensor or a vacuum leak
411 = idle speed not controlling properly, usually due to a sticking iac but could be vacuum leaks too
225 = knock sensor not tested

based on your description of symptoms and the stuff you have already changed, I would conclude you have a fairly serious vacuum leak. There are a bunch of little vacuum hoses on the top of the engine, all of which are 20+ years old and have seen better days. I would work through all of them carefully to see where you may have leaks.

Once you find and fix all those leaks (however many there may be) then reset codes and drive a week, then pull codes again. At that point you may have solved all your driveability issues, or you may still have a sticking iac.

Note that your secondaries not kicking in until 4500 could be that the tach reading is off.

 

[RookieSHO]

please also pull the key on engine off codes - those are the stored codes and are often way more valuable.

412 = idle speed not controlling properly, usually due to a sticking iac but could be vacuum leaks too
172 = lean on right bank, either bad oxy sensor or a vacuum leak
136 = lean on left bank, either bad oxy sensor or a vacuum leak
411 = idle speed not controlling properly, usually due to a sticking iac but could be vacuum leaks too
225 = knock sensor not tested

based on your description of symptoms and the stuff you have already changed, I would conclude you have a fairly serious vacuum leak. There are a bunch of little vacuum hoses on the top of the engine, all of which are 20+ years old and have seen better days. I would work through all of them carefully to see where you may have leaks.

Once you find and fix all those leaks (however many there may be) then reset codes and drive a week, then pull codes again. At that point you may have solved all your driveability issues, or you may still have a sticking iac.

Note that your secondaries not kicking in until 4500 could be that the tach reading is off.

I replaced the vacuums hoses on the secondaries and on the fuel pressure regulator and on the smog that goes to the intake manifold, I replaced the IAC with a Standard AC20T (it had Standard AC58T before which wasn't quite working right) and now the car working a little bit better, also I replaced the tps sensor with a BWD EC3019 and my car is responding a little better



I redid my tests and this is what I got

KOEO
111

KOER
536
521

Continuous
157
172
176

Engine balance test code is 90

if the tach reading is off then I won't worry too much about it

 

[rubydist]

111 = all is well
536 = brake on/off switch shorted to ground (do your brake lights work?)
521 = wheel not turned during test
157 = mafs signal is grounded
172 = lean on right bank
176 = lean on left bank

If you reset the codes and are still getting these, then you have a problem with the mafs or the wiring to the mafs. Since the mafs and the tps are on the same power circuit, it will either be the mafs sensor itself, or the signal line from the mafs to the pcm. Note that these engines will not run correctly with the mafs code, so this must be resolved.

The lean codes are very possibly due to the mafs not reading the airflow correctly. I would focus on the mafs code first.

 

[RookieSHO]

111 = all is well
536 = brake on/off switch shorted to ground (do your brake lights work?)
521 = wheel not turned during test
157 = mafs signal is grounded
172 = lean on right bank
176 = lean on left bank

If you reset the codes and are still getting these, then you have a problem with the mafs or the wiring to the mafs. Since the mafs and the tps are on the same power circuit, it will either be the mafs sensor itself, or the signal line from the mafs to the pcm. Note that these engines will not run correctly with the mafs code, so this must be resolved.

The lean codes are very possibly due to the mafs not reading the airflow correctly. I would focus on the mafs code first.

I swapped the MAF Sersor from my family/Parent's 94 ATX SHO Since I know that car is working good and clear the codes then run it for a couple of days, I had to clean the sensor too since my car was acting up when I tried to accelerate then it went away after it has been cleaned, now my car is starting and running a lot better (it goes up to 2,000rpm then down to 1,000rpm and it didn't even act like it was going to die so it was purring like a kitten ) then before I swapped the MAF, I ordered a new MAF system at rockauto.com for $59.79 (Advance auto parts was charging $180 new and $86 for Remanufactured)

my brake lights work so I didn't do the test right


I redid my tests and this is what I got

KOEO
111

KOER
111

Continuous
217


I swapped out my original ignition coils with the New BWD E97 I had laying around in my room, I cleared the codes and run my car for a couple days to see if I get anymore codes or not



I redid my tests and this is what I got

KOEO
111

KOER
111

Continuous
111

 

[rubydist]

excellent!

 

[RookieSHO]

I tried the new Cardone 869502 MAF but it constantly rev my car up and down at idle so I'm going to have to returned it and find a good oem brand

do you know any good brands that will work well?

 

[luigisho]

I always went with used good working ones. Aftermarket is wonky for these. You have a Ford part number? If you can get a new OEM one still on a shelf somewhere, that would be preferable. If you post in the wanted to buy section or with the facebook group I bet someone has a good used one sitting in their garage.

 

[zoomlater]

Type in the part number from your original MAF into ebay. I thought there were some that matched my 94 MTX car on there that were Ford NOS parts