Grrr, Check Engine Light, likey causes?

[ILikeSix]

So I'm making progress with the new to me TR (86 T type GNX clone), fixed a couple leaks( still the trans cooler lines to replace:redface worked with the paint, got some refurbished GTA rims from a great Ebay seller (Rodzgnautoparts, Jesse is his name) All in all good progress. Driving yesterday the "Service engine soon' light popped on and driveabilty went into the toilet. It will run but anything more than 1/4" of throttle makes it choke/sputter/cough:frown: I looked for loose wires/vac lines, all seems intact. MAF was replaced less than 500 miles ago, I threw a TPS at it because I had one (set the resting value to 40). What are the symptoms of a bad CPS? Is there a way to pull the codes to see why the CEL is illuminted?

Not sure what to try next, any hints as to the likeliest causes?

Sux being a TR NooB:frown:


Alan

 

[charlief1]

GM OBD1 cars are easy to get a code out of. Go to Autozone and they have a key that they give out for free. It goes into the ALDL port located under the dash on the drivers side. Once you plug the key in it will cause the check engine light to flash like moris code.

It will flash in a number sequence. It will repeat each code three times and then move to the next code. So a code 12 would be a single flash with a short pause followed by two flashes and a long pause, then repeat two more times and go to the next code. Hope that helps you.

 

[mikestertwo]

Just jumper pin "A" to pin "B" on your ALDL connector, turn the key on but don't start the car. The engine light will flash "12" three times then it will flash any error codes. They will also flash three times.

 

[Roger]

Best advice anyone can give: Get a Scanmaster.
The Scanmaster will give the error codes & is invaluable for tuning.
Other scan tools are also available & some are better than others (even better than Scanmaster), however, some are more expensive.

 

[Phoneguy]

Check your balancer bolt, if loose it will cause the crank sensor to hit.

Bryan

 

[novaderrik]

Just jumper pin "A" to pin "B" on your ALDL connector, turn the key on but don't start the car. The engine light will flash "12" three times then it will flash any error codes. They will also flash three times.

yeah, the only "diagnostic" tool you need for GM OBD1 cars is a straightened out paper clip. if the ecm isn't junk, it will tell you what codes it has stored. that won't always tell you what's actually wrong, but it will tell you what the ecm thinks is wrong.

 

[ILikeSix]

Thanks for the great responses, good ideas.

The car has a Scanmaster but my experience with it is limited.:redface: I did notice the 02 Milivolts drops WAY down when the conditon occurs. Like cruise is 500-700 then when the stumble hits, 30's and 40's. Maybe this is a fuel delivary issue? IFP is rock solid on the rail mounted gauge but that doesn't say much about what is happening during load/driving conditions. My FP gauge that has a rubber line is some distance from my house, I'll grab it tomorrow.

So my next two uninformed questions would be:

How to tell which pin is A and which is B on the ALDL, and alternatively, how to access codes with the Scanmaste?. I've clicked around on it plenty but without a tutorial, it's a shot in the dark:frown:

Phoneguy, the crank pulley is and aftermarket underdrive set up and it does have an alarming amount of wobble to it:frown: Would the motor start/run with a crushed CPS?


Thanks again

Alan

 

[Phoneguy]

Car will run better at idle than at higher rpm with crank wobble. Crank bolt needs about 230 ft lbs of torque. Also put some lok tite on the threads.
If the reluctor ring is damaged or has moved you will need to address this before the car will run right.

Bryan

 

[ILikeSix]

I replaced the fuel filter, why the F do they put it right on the framerail Getting the fittings restrated while fuel drips on you is no fun Pressure is rock solid even while the stumble occurs. My brother and I devised a way to view the fuel prssure gauge while driving, it was probably illegal and marginally dangerous but worth the risk So I think we can elimnate fuel starvation as the cause of the stumble.

Bryan, the crank bolt is not loose and I unplugged the GM weatherpack three wire connector that leads to that black round housing above the crank snout, that's the CPS right? Car still runs with it unpluged so not sure.

I think the ScanMaster is giving me codes 23 and 34, or those are some other values I don't understand. I'm gonna look for some scanmaster instructions online I suppose.

Still not sure which is A and which is B on the ALDL so not gonna go jumping it unitl I can find out.

Thanks again for any responses and ideas

Alan

 

[mikestertwo]

Still not sure which is A and which is B on the ALDL so not gonna go jumping it unitl I can find out.
Alan

Pin "A" is the top right terminal. "B" is the terminal just left of it. Code 23 is the MAT sensor, code 34 is the MAF sensor.

 

[Phoneguy]

I believe you have the cam position sensor confused with the crank position sensor. The crank sensor is to the right side of the crank where the timing tab is located. The car will not run with this disconnected. take the sensor off and see if it has made contact with the reluctor ring on the inside of the balancer.

Bryan

 

[ILikeSix]

Sigh, you're prolly right Bryan it seemed kinda high up on the motor to be reading the crank, dont'cha just hate having to train the new guys Since code 34 is the MAF, I'm gonna throw ANOTHER one of those at it:redface:, found a local reman for $85+$31 core. What is a MAF translator for? I see it in a bunch of sig lines...

Alan

 

[we4Mateo]

Sigh, you're prolly right Bryan it seemed kinda high up on the motor to be reading the crank, dont'cha just hate having to train the new guys Since code 34 is the MAF, I'm gonna throw ANOTHER one of those at it:redface:, found a local reman for $85+$31 core. What is a MAF translator for? I see it in a bunch of sig lines...

Alan

The translator allows you to run a more modern, accurate, and more reliable newer style MAF such as one from an LT1, LS1, or even bigger MAF.

 

[ILikeSix]

A second rebuilt MAF within 500 miles fixed the problem:redface: I am liking the idea of running a larger/modern LS MAF and a translator and since I don't care for the shiny chrome CAI kit on the car, upgrading to a larger size would have aesthetic benefits too Wrinkle black finish FTW

Not sure if it was involved in the codes being thrown but I found a *finger tight* spark plug on the passenger side nearest the firewall (number 5 right?) It was so loose, it was actually rattleing around at idle Threads on the plug look fine and it tightened up (after cleaning all the blow-by goop off of it) securely but I gotta wonder if the threads in the head took some abuse:frown: Nice to have a motor that runs on all six now:redface: and to be rid of the PFFTT PFFTT PFFTT sound that I thought was the passenger side header leaking...

Great progress yesterday, now that it doesn't want to die on every throttle tip in and makes actual power, I'm enjoying driving it I love the things guys who pull up next to you in traffic say:biggrin: Driving a GN, you really are the envy of a lot of guys who have always wanted one. The young guy working the gate shack actually got weak in the knees as he gushed about it being the coolest car that has ever been built when he saw it for the first time yesterday. Of couse I obliged him with a small smoke show and stepped the rear out 30 degrees when I left. It *almost* came around on me:redface: That woulda really impressed him...


Alan