1992 Mustang - No Data? Fixed I guess

[protraxrptr17]

I'm working on a 92 Mustang GT. I don't work on too many non OBD II vehicles so bear with me if this is a stupid question, but why can't I find any engine data? I have a Snap-on Modis.

[steven kiser]

it's pre 95. what readings are you getting if any at all. the modis may be too advanced to give you what you're looking for. bear with me, i'm a bit foggy here. on the data plug there are two tan wires. in the past i've had problems when one of them rotted at the plug and another biggie is the ground wire rotting off on the engine side of the harness. at best the information you retrieve will be embryonic to what you're use to. what's the issue with this car?

[protraxrptr17]

I don't even have an option. Just codes menu, functional tests, super star II mode, and troubleshooter. Customer complaint is engine smothers out intermittently. Fuel pressure is good. The car runs kinda rough and black smokes a little when you get down on the throttle after its been idling. Hard to start when cold too. I'm sure this car has multiple problems. Please don't tell me I'm gonna have to back probe all the sensors to get the data I'm looking for.

What is super star II ?

[steven kiser]

before you get in too deep there is an air charge sensor next to the plenum chamber about 1/2 way down. this could be the issue. if the little cage around the reader and it's all gummed up replace it. this also sounds like a mass air flow issue. if i had to guess i'd lean towards the air flow sensor.

[liljoe]

I would check the orange ground wire for the oxygen sensor, I think it bolts to the back of the intake, if it is off it will car to run rich, esp at idle and right after.

[protraxrptr17]

Is the air charge sensor a two wire black plastic sensor that threads in between the 5 & 6 injector? What does this sensor do? Is it basically an IAT sensor?

I guess I'm gonna scope the maf and the fuel pump which was my first thought when he told me the symptoms. What a dumb idea to have a fuel injection system with no live data.

[liljoe]

Don't forget to check the orange wire for any voltage whit car running, it will make a big differance, I have seen this a bunch, it is easy to miss this wire when doing repairs that require the removal of the upper intake.

[a&mauto]

Is the air charge sensor a two wire black plastic sensor that threads in between the 5 & 6 injector? What does this sensor do? Is it basically an IAT sensor?

I guess I'm gonna scope the maf and the fuel pump which was my first thought when he told me the symptoms. What a dumb idea to have a fuel injection system with no live data.

Yes, that is it, an IAT sensor. And yes, thats how we used to have to do diagnostics, pin-point tests. Thats why we have breakout boxes for those cars. It was faster to disconnect the ecm and run a breakout box in line. We did our tests (and still do on these cars) by pin number. Fun Stuff

[protraxrptr17]

The orange wire is grounded. The sensor was clean, but read 4.5 K ohms. I'm assuming that is too much. Waiting on a replacement to get here now from slow'reilly CB didn't have it.

[steven kiser]

never assume, the sensors on these beauties are tied in in groups. i've seen shorted a/c clutches on these cause problems. if the sensor is sparkling clean I'd check and see if some one cleaned the plenum with carb cleaner. back then it was a big no no and would mess up the sealant inside the plenum. i would still lean towards the mass air flow sensor. i'm trying to remember if these had the two sensors on or around the thermostat housing. i believe the casing colors were green and brown. these are the temp sensors. one is guage and the other is the sensor for the pcm. i'm not sure what one's for the pvm but if this engine has this set up you may see the temp guage reading fine but the pcm may still be reading cold. on a side note i kinda chuckle when someone starts to talk about how difficult diagnostics have become. i remember this era of diagnostic procedures and shudder.

[protraxrptr17]

Yeah, I would much rather work on newer stuff. I have found out that just about every shop in town has worked on this car, and every sensor, the fuel pump, regulator, and even the pcm have been changed. I found that it has no oxygen sensors. I guess somebody figured they weren't needed. I did something I wouldn't normally do. I just welded the EGR shut and told him to go run it. I drove it around all day and couldn't duplicate the symptoms and so much has been done to the car that it's just not worth it. The ECT had been changed too. I know that really doesn't mean anything though.

[liljoe]

It doesn't stand a chance of running right without oxygen sensors in it.

[protraxrptr17]

Yeah, I know. The real complaint was for the smothering issue, so I figure as long as I have fixed that, I have won. I didn't hear from him today, and I made him pay me for 2 hours of diagnostics before he took the car so I'm sure he'll call if it does it again.

[steven kiser]

a real quickie here i completely forgot about. i've seen quite a few of these with the performance chip in it. you could purchase these and install them easily. they would shut out all data.

[protraxrptr17]

Guy called me yesterday and is ecstatic. He is confident the car is fixed and wants to bring it back for me to reinstall the oxygen sensors that I recommended. So I guess the EGR was the problem. I have no idea why it was opening, but given the past history of this car, and it's value, it's not worth pursuing.