88 GMC K2500 Stalling Problem

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Hi,
First, a little history- Last summer I had to replace the fuel pump in the tank.... not fun, but not too bad. I also replaced the fuel filter. It has
been running good until this week. It starts ok and idles fine for a TBI 350 engine. I can rev it and it's fine but, when I put it in gear it goes forward and then stalls. It starts right up again and stalls the same way. My question is this related to last years pump replacement or something new?
Thanks, Tim
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Sure sounds pumpish to me. Had an 88 S-10 that had so little left by the time we got it home from 300 miles - that it barely moved - we definately had to avoid hills the last 20 miles or so. Do you run with less than 1/4 tank? Even though the return gas is supposed to wash over the pump, it's definately better cooled when over 1/4 tank full. Elliott
Tim Duerst wrote:

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do you have any DTC? -Bret
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Bret,
Can you tell me what's DTC.....? Sorry to be ignorant.
Tim
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He's referring to "Detected Trouble Codes" from your truck's computer. Usually they also set the Ceck Engine Soon light on the dash - but I think there are a few that don't. Some AutoZone's (not Advanced Auto) will read them for you, or any shop - though careful w/ the price it's a 15 minute procedure (max) and a shop here in WDC charges $70 for it. Elliott
Tim Duerst wrote:

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diagnostic trouble codes... on an 88 they'll be 2 digit codes that you get by connecting two pins (can't remember which off hand) on the ALDL connector and counting the flashing check engine light.
they're very helpful.
Bret

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Thanks, will the procedure be in manuals like Chilton and so forth? or is there a tester that I could get? In the mean time would you even hazard a guess?
Thanks, Tim
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Tim,
Sorry I wasn't paying attention to the year (pre 96 you can read without a special reader). The OBD1 diagnostic connector is by your knees in the driver seat. Pin A is ground and pin 5 is the Diagnostic terminal. I think these are usually the top right of the connector, unless it's mounted upsidedown (look for the tabs and key I depicted with the | and the _ characters): | F E D C B A _G H M_
And FYI the pins are: A = Ground B = Diagnostic Terminal C = AIR (if used) D = Check Engine light (if used) E = Serial data (requires a reader) F = TCC (if used) G = Fuel Pump (if used) H = Brake Sense speed input M = Serial Data (4 cyl only, requires a reader)
So to read your DTCs, put a paper-clip or some sort of jumper between pins A and B. Turn on the ignition and count the flashes. For example, a 42 would blink 4 fast, pause a moment and then blink 2 times. The sequence will begin and end with a 12. Each code repeats itself 3 times - so be patient.
You can report your codes back to the NG and posters here will tell you what they mean. You can also search on "OBD" and "Chevy" and you will find lots of info. For example: http://www.troublecodes.net/landrvr / .
Elliott
Tim Duerst wrote:

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Hi,
Thanks for the info, it worked well but, all it flashes is the number 12. Am I suppose to start the truck? All I did was turn the ignition on.
Tim

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Hi,
Thanks, I figured ignition on meant what it said but, I'm new to this kind of troubleshooting and had to ask.

short distance (5-10 ft).

when I rev it though. It forever has idled rough until it warmed up. I kinda excepted it ( the rough idle )with what I've read in here over the years.

Thanks for everybody's help so far.
Tim

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die like the ignition is switched or, a rough, stumbly kind of stall?

my 88 idles smooth until the engine warms up enough to let the EGR valve leak.... (that damn thing keeps getting pushed back on the to-do list)

the skinny pedal is the gas pedal.

an engine in good condition wil have a steady needle at around 17 in/mg at idle. go to a parts store and pick up a haynes manual for your truck, they have a decent section on using a vacuum guage to troubleshoot.
-Bret
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Ah, skinny pedal kinda ...makes ...sense now LOL!

Tim
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Tim, You say it dies like you shut off the key. Does it also do it in reverse or just drive? Does it also do it if you put it in drive and hold the brake? How about if you hold the brake and give it some throttle? From the description I'd almost think it was a problem with the wiring going to the ignition system from the firewall. Like a loose connection or a wire that is grounding out when you put it in gear. Does this vehicle have an security system?
--
Steve Williams

"Tim Duerst" < snipped-for-privacy@mhtc.net> wrote in message
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it will run with the aldl grounded. this puts the system in back-up spark and fuel mode. base timing and no fuel trim available.
Re: 88 GMC K2500 Stalling Problem Group: alt.autos.4x4.chevy-trucks Date: Tue, Apr 13, 2004, 7:02pm From: snipped-for-privacy@nope.com (Doc)
wrote: :|> :|> >:|Hi, :|>>:| :|>>:| :|> >:|First, a little history- Last summer I had to replace the fuel pump in :|the :|> >:|tank.... not fun, but not too bad. I also replaced the fuel filter. It :|has :|> >:|been running good until this week. It starts ok and idles fine for a :|TBI 350 :|> >:|engine. I can rev it and it's fine but, when I put it in gear it goes :|> >:|forward and then stalls. It starts right up again and stalls the same :|way. :|> >:|My question is this related to last years pump replacement or something :|new? :|>>:| :|> >:|Thanks, :|> >:|Tim :|>>:| :|> :|> do you have any DTC? :|> -Bret :|
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snipped-for-privacy@webtv.net (pete carb) wrote:

Ummmm... grounding the ALDL with the engine running puts the system in "Field service mode," fixed timing above base and the CE light indicates open or closed loop and rich/lean status. Jumpering pins "A" and "B" with a 3900 ohm resistor will put the system in back-up spark and fuel mode.
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Ok, I took the vacuum at idle and at 3000 rpm it stays steady at 18. I did replace the egr valve. The other one was froze up. Still does the same thing. The funny thing is that I can go farther in reverse than forward. Any more suggestions would be helpful.
Tim

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1: I think it's your EGR valve. 2: Starting the truck like that is generally considered a BAD thing. I have heard that it should NEVER be done, and I have also been told that it can. If your not getting any codes now though, then you wont get any if you start it. Even then, a fuel pump wont throw codes. 1A: If/when it was running JUST before this (I'm assuming it had a period of degradation) did it run just fine on the highway, but poor at low speeds and plain rotten at idle? If so have you checked your EGR valve for operation? If it gets stuck open (these might as well have been designed to get stuck open) then the exhaust gases being introduced into the engine will cause it to stumble at idle. It's a super simple R&R if that is the problem.
~KJ~

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You can ground the terminal after its running to put it into field service mode, I dont know when that was discontinued though.
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