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1993 'Burb Stalling Problem


Fryall4
05-30-2007, 05:41 PM
Hello I have a 93 Chevy Suburban, 4X4, AT, A/C, All Power. The problem has been going on for months now and over the past month, getting worse. The truck will stall out when stopped at a light in gear. It starts right back up every time. I have been dropping it into N lately but it has even started to die sometimes when I do this. I have 220K miles on the truck, 22K on the new motor, 19K on the new transmission (4L60E) and 1100 miles on the new rear end. No codes come up when the truck stalls and dies. I have changed the;
Fuel Filter
IAC (Idle Air Control) Valve
Cap, rotor, plugs
TCC (torque convertor clutch lock up) Solenoid

Checked for vaccum leaks
pulled the throttle body and cleaned it up (no bad carbon)

The truck runs great other then the stalling problem. The problem has been becoming worse as time goes on, and it seems like it is searching at idle for the proper rpm level. I guess I have to try the EGR valve and then the crank position sensor, maybe even the ignition control, but any advice or suggestions would be greatly appreciated. After the $1400 rear end and the tcc solenoid, money is quickly becoming an issue. Fry-

Fryall4
05-31-2007, 09:34 AM
I am going after the EGR valve today, does anyone have any other ideas of what I should try first? :banghead: Fry-

2000CAYukon
05-31-2007, 10:24 AM
You don't have a crank position sensor.

Stalling on a TBI engine can sometimes be a weak pickup coil in the dist. You should also check for a worn dist shaft bushing (with the cap removed, can you move the shaft side to side).

On my 90 GMC truck, I found 2 vacuum leaks that helped the idle quality. In my case, it never stalled but the idle hunted up and down.

1st leak was the vacuum hose to the MAP sensor. 2nd leak was at the PCV gromet in the valve cover. The gromet had become hard and was not sealing well.

//2000CAYukon

Fryall4
05-31-2007, 12:27 PM
Ahh thanks 2KYukon, I would have sounded quite the fool asking for a CP sensor at the parts store. I will look into the pcv grommet...actually come to think of it, when I cleaned out the throttle body the other day I saw the tube going to the valve cover (driver-side) was broken and someone had put a small sleeve of rubber hose over it to connect the pieces. I figured it was good and didn't detect a leak there. Hmm :uhoh:

Fryall4
05-31-2007, 01:38 PM
Alright, just ordered an EGR valve and gasket, PCV valve and grommet. I will be installing them shortly with testing in between to see what the problem was if it gets cleared up. Cheers-

Fryall4
05-31-2007, 06:38 PM
Ok, it is a no-go with the EGR and the PCV valve. My truck did not have a PCV valve, it does now but did not help a thing. I replaced all the plug wires today with no help. Cleaned the connections on the battery, the ground near the battery and the ground on the intake manifold = Nothing. Checked the play in the distributor and I could not move it side to side. The only time I got it to run half way descent was when I unplugged the throttle position sensor. The rpm's were not right and the check engine light was on but at least it did not die in gear. Unplugging the MAP sensor did nothing to help.

What do you all think would be the next logical thing to check? Ignition Control? Computer? Thanks a lot, Fry-

Fryall4
06-01-2007, 12:25 PM
I am going after the Ignition Control Module today. I have been doing a lot of reading and some fingers point at this part as a possible culprit. After that I think I will go with the Coolant Temp Sensor, and then the coil. I figure new parts won't hurt. Fry-

2000CAYukon
06-01-2007, 12:47 PM
I am going after the Ignition Control Module today. I have been doing a lot of reading and some fingers point at this part as a possible culprit. After that I think I will go with the Coolant Temp Sensor, and then the coil. I figure new parts won't hurt. Fry-

The pickup coil inside the dist can also go bad and cause a stalling problem. Something to think about when you go after the ignition module.

The ignition module converts the signal from the pickup coil from AC to DC. If the pickup coil is not giving the ignition module a good signal, the ignition module is not going to give a good signal to the ECM.

//2000CAYukon

Fryall4
06-01-2007, 04:00 PM
Thanks 2k, I'll pick up both parts today, give them a try and post back. Fry-

2000CAYukon
06-01-2007, 05:00 PM
Thanks 2k, I'll pick up both parts today, give them a try and post back. Fry-

Just to let you know, you need to pull the dist and remove the shaft to replace the pickup coil.

//2000CAYukon

Fryall4
06-01-2007, 07:00 PM
2K It is really nice of you to help me with this, and yes, that was going to be my next question. I replaced the module, didn't help, and then was looking around trying to figure out how the heck to get the magnet and pickup off the shaft. Anyway, I am sure the neighbors appreciate me quitting for the day (my rear end was hanging out the hood, LOL). I will pull the distributor tomorrow and replace the coil pickup.
I read some stuff earlier today about a tan wire a guy disconnected (he has a similar problem) and it got his truck to run a bit better. While hanging out in my engine bay today, I saw a single tan wire with a connector near the fuses and relays (pass. side firewall). I disconnected the wire, and while the check engine light comes on and the idle is even lower then it was before it stays running and doesn't stall. Does anyone have an idea of what this wire is and what affect it is having on the runability of the motor? Fry-

2000CAYukon
06-01-2007, 07:25 PM
2K It is really nice of you to help me with this, and yes, that was going to be my next question. I replaced the module, didn't help, and then was looking around trying to figure out how the heck to get the magnet and pickup off the shaft. Anyway, I am sure the neighbors appreciate me quitting for the day (my rear end was hanging out the hood, LOL). I will pull the distributor tomorrow and replace the coil pickup.
I read some stuff earlier today about a tan wire a guy disconnected (he has a similar problem) and it got his truck to run a bit better. While hanging out in my engine bay today, I saw a single tan wire with a connector near the fuses and relays (pass. side firewall). I disconnected the wire, and while the check engine light comes on and the idle is even lower then it was before it stays running and doesn't stall. Does anyone have an idea of what this wire is and what affect it is having on the runability of the motor? Fry-

The Tan wire is for setting the timing. Disconnect the wire, set the timing to zero and reconnect the wire.

When you disconnect the wire, all timing advance is stopped so it will not run as well.

I have an extra dist with a new pickup coil and module but you would have to drive to San Jose to get it.

Good Luck.

//2000CAYukon

Fryall4
06-01-2007, 11:20 PM
Ahh, I see. The truck did run pretty cruddy, but hey, no stalling. Is replacing the pickup a fairly straight forward job? I am pretty sure I can figure it out unless there is some wizzard of Oz, tap your heels type of stuff going on. Lol, I may take you up on that distributor if things go badly tomorrow, hopefully not, but I appreciate it.
By the truck not stalling with the wire disconnected, does that tell me anything? Is the ring covering the pickup coil supposed to spring forward and back because when I was in there I could physically move it but there was no spring action to speak of, maybe broken spring(s)? If it is indeed part of the advance I would have to think it was fine, wire plugged in the truck stalls but runs great off idle. The wire disconnected no stalling but runs mediocre off idle. Just swinging at the fences here. Thanks again, Fry-

2000CAYukon
06-02-2007, 11:01 AM
I missed the fact that it does not stall with the EST Bypass disconnected. If the pickup coil was bad, it would probably stall even with the wire disconnected.

What is timing set at? This sounds more like a vacuum leak to me. The EGR solenoid and MAP sensor should hold a vacuum and the hoses should be inspected.

I found the MAP vacuum hose was not holding a vacuum and was part of my idle issues on my 90 K1500.

//2000CAYukon

Fryall4
06-02-2007, 02:20 PM
Hey 2K, well, as suspected I changed the pickup coil, the one installed was hammered, Ill try and post a picture. I reset timing (0 degrees with tan wire disconnected) and still have the same thing. I have the battery cable pulled right now waiting on the computer to reset, hoping this will help but will not hold my breath. Ill check and make sure 0 deg. is what it is supposed to be, Ill post again with my findings. Fry-

Fryall4
06-02-2007, 02:35 PM
Heres the pic, looks like it got real hot at some point

http://www.mediafire.com/imgbnc.php/be83fb241e87f9bef480bf4b9263c57a4g.jpg

Fryall4
06-03-2007, 12:13 PM
Is there anything more to resetting the computer then pulling the battery cable for a while? Is there a certain procedure when starting the vehicle ie, idle for a while, raise rpm's? Thanks a lot, Fry-

2000CAYukon
06-03-2007, 12:46 PM
Is there anything more to resetting the computer then pulling the battery cable for a while? Is there a certain procedure when starting the vehicle ie, idle for a while, raise rpm's? Thanks a lot, Fry-

Disconnecting the battery will reset the ECM. Relearning of the fuel trims can take about a week of normal driving.

Hooking up a scan tool to see Sensor values, fuel trims and 02 Sensor activity would help right now.

//2000CAYukon

Fryall4
06-03-2007, 07:44 PM
Thanks 2K. My uncle has a Snap-On scanner, we had it hooked up before to see if there were any stored codes which there wasn't. I can try and get together with him again and check on those values. I am about $300 into this now and may just take it into my mechanic. I wanted to avoid that. It is my daily driver and as it is now, I don't even want to drive it, I have kids. Anyway, I may swap out the coil just to test that theory while I am waiting to see when the mechanic can get it into the shop. Anything else come to mind? Fry-

Fryall4
06-04-2007, 04:16 PM
Coil is not the problem. Idle still WAY too low, running 250 rpm's in gear, about 400 rpm's in Park. I am at a loss. I am left thinking Coolant temperature sensor, some obscure vacuum leak, computer, or catalytic convertor. Am I wrong? Anyone? Thanks again, Fry-

2000CAYukon
06-04-2007, 06:59 PM
Coil is not the problem. Idle still WAY too low, running 250 rpm's in gear, about 400 rpm's in Park. I am at a loss. I am left thinking Coolant temperature sensor, some obscure vacuum leak, computer, or catalytic convertor. Am I wrong? Anyone? Thanks again, Fry-

A scan tool will show you what the temp sensor is reporting to the ECM. If you unplug the sensor (in the intake manifold near the tstat housing), it will tell the ECM that the engine is running cold and it should increase the idle speed. What happenes if you do this?

Is fuel coming out of both fuel injectors?

Unplug the 02 sensor, remove it and start the engine. If the cat is plugged, it should run a better with the 02 removed. If the cat was plugged, it would not run well at highway speeds either.

Testing the fuel pressure on the TBIs is a pain; however, you need to test the fuel pressure and make sure it is within spec (9 to 13 PSI). Or take it somewhere to be tested.

//2000CAYukon

Fryall4
06-05-2007, 10:07 AM
I see 2K, you are a very wise person, thank you. Fuel is coming out of both injectors, and I will check on the O2 sensor asap and the coolant temp sensor today. I am taking it to my mechanic today, and he can test the fuel pressure for me, I will know more in a day or so. Fry-

Fryall4
06-06-2007, 03:05 PM
I talked to the mechanic yesterday, he didn't have a lot of time to devote. He said he was leaning towards a computer problem or a transmission pressure switch problem. He was sort of stumped as most of his tests came up negative. He noticed an issue with the IAC valve when hooked to the scanner. He said it was showing activity on one of the coils at idle, which I guess is not supposed to be. I could be mistaken, he was throwing a lot at me, and I tried to remember as much as I could. Anyway, he hasn't called today, but I did tell him yesterday that the truck was of little use to me as it was so he may not have put it high on the priority list for today. Fry-

bluechevelle
06-10-2007, 12:04 AM
I had a similar problem with my '94. It ended up being the temp sending unit in front of the throttle body. Doubt it is your problem from what I'V read, but for $11 it's worth a try.

Fryall4
06-11-2007, 10:04 AM
I appreciate any help and suggestions Bluechevelle. I haven't heard back from the mechanic yet, so it must not be the best of news whenever that comes. Such is life huh? :)

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