1993 K1500 runs terrible when hot

[Schurkey]

Originally Posted by Thor1993

Schurkey -There is a rubber line at the bottom of the firewall it connects the steel line from the TBI to the steel line that runs to the tank. I am not sure if the rubber line is factory or not. When the main fuel line rusted out a few years ago I went to GM and got all new replacement lines to the firewall. I don't remember cutting a steel line and putting a rubber line in. I usually don't cheat on fuel pressure stuff. Isn't rubber line Ok on a 13 psi fuel system?? Anyways, I sure hope you didn't think I was being a smart ass by posting the picture....but that is actually what I used.
Greg

I wouldn't expect ordinary rubber hose on this vehicle. Mine ('88 K1500) has hard plastic tubing, steel tubing, or "steel-braided" hose. No plain rubber.

If the rubber hose and clamps are specified for fuel injection, you're likely OK. Plain "carburetor style" hose is not acceptable, neither are ordinary worm-clamps.

[Thor1993]

News Flash!!!!!
The new AC Delco distributor arrived today. I inspected it, lubed it and installed it. Then I set the timing and went for a test drive and……..drum roll please… It fixed it….well I went for a 10 mile ride and it ran better than it has in 2 months. I think t is 85% fixed. There is still something not perfect. But I am really pleased. The old distributor was a GM. It had same P/N as new one. The end play on the old one was about .062 and .052 on the new one.


Somebody is getting tired of me working on my truck all the time.

Anyways here is a picture of the truck. As you can see it has been earning its keep plowing. It plows fine and I use it all the time plowing. That pile of snow behind the truck is all over the edge of my driveway. The plowing has slowed my finding the problem because I need the truck every time it snows and here in Michigan that has been a lot lately.

Here is an update on other issues with the truck.
Correction on advance – I marked the line on the harmonic balancer white a white marker. The timing does not advance when I rev it up as I posted earlier.
Exhaust manifold – it has been too cold for me to go to the junk yard looking for a replacement manifold. The crack is big but closes up when the motor is hot. I want to replace it anyways. Here is a picture of the crack.

TBI- I think it is very dirty! I will get into that next, rebuild the regulator and send the injectors out for a rebuild/test.
Knock sensor – I found the knock sensor. On the V6 it is under the distributor. I was looking for it near starter but that is where it is on the 5.7 L engines. I will check that also.
Spark plugs – I think I will put new ones in. They have been through hell the past 2 months.
The vacuum gage says no problems but it just seems to me that it comes down too slow after you rev it up.
Anyway’s Thanks for all the great advice form you guys. I will keep doing updates as I go further.
Greg

[Schurkey]

Originally Posted by Thor1993

I think t is 85% fixed. There is still something not perfect...

...Correction on advance – I marked the line on the harmonic balancer white a white marker. The timing does not advance when I rev it up as I posted earlier.

Did you re-connect the single-wire connector?

[Thor1993]

OK, I redid a timing advance check with the wire connected, it advances when I rev it up.

[Thor1993]

Well I spoke too soon, I went to drive the truck to work today and after it warmed up it ran horrible again. I will start working my way down the list of more things to check.
It is so odd, we plowed with it for 2 hours straight over the weekend and it never missed a beat. But out in the highway no power, poping and missing....

[rhandwor]

I had a Chevy and a valve guide got worn and it would run fine then the valve would twist and it would miss. With the valve cover off you could watch what was happening. When you do your exhaust manifold I would do a compression test. If you put some oil in a low cylinder and the compression doesn't change I would look at the valves sometimes a nut will come loose. They use lock nuts get a new one if loose.

[j cAT]

Originally Posted by Thor1993

Well I spoke too soon, I went to drive the truck to work today and after it warmed up it ran horrible again. I will start working my way down the list of more things to check.
It is so odd, we plowed with it for 2 hours straight over the weekend and it never missed a beat. But out in the highway no power, poping and missing....

I posted this on feb 10, 2014 " the exhaust manifold crack my be the problem. with a crack the KS will retard timing . also the O2 will report a lean condition to the computer. this will be noticeable after the open loop ends and the closed loop begins. "

having seen your crack you wasting time and money chasing ghosts !

[Thor1993]

j cAT - I trust you! really! and I appreacoaite your help!!!

But it is at the moment 10F outside and the snow is 3 feet deep. I just don't have the motivation to get to the junk yard and get a manifold yet.....

You are totaly right about chasing ghosts and in general I don't do the shot gun approach by throwing money at it but the coil pick up in the distributor was cheap and then I found the bastard distruibutor so I bought a new one.

Maybe I should just give in and buy a new manifold because at the current rate of snow and cold it will be June before I get to the junk yard.
Greg

[Thor1993]

rhandwor - Thanks for idea. I have the compression test on my list of things to check. I will look for valves also. (and a bad cam at the same time when I have the valve cover off.)

I am thinking hard about buying a new manifold and not waiting to get one at the junk yard also.

With the snow we have had I can't take this truck out of service so I have to plan out working on it between plowing.
Greg

[Thor1993]

Hi Guys,
Well I thought I better do some testing before I invest the time and money into a new exhaust manifold. So tonight I did a compression test. The motor was warm but not hot like the manual says but I ran one anyways. The results are cylinder #1, 2, 3, 5 & 6 were all 90-120psi on the first stroke with most about 110psi and 160-175psi on the 5th stroke. Cylinder # 4 was 75-80psi on the first stroke and 150-155psi on the fifth stroke. I put some oil in cylinder # 4 and re re-ran the test and it was 120 on the first stroke and 200psi on the fifth stroke. Spec is all psi readings within 20psi. So for a truck with 180,000 miles not too bad. I wish #4 was alittle better.
Next I am going to pull the valve covers and make sure the cam and valve train is working. If not I can do the exhaust manifold and other repair all at once.
Also, the plugs are AC Delco and the wires said "Standard 7mm". What do you guys think of Standard spark plug wires??
Take Care and THANKS FOR POSTING!!!,
Greg

[rhandwor]

I've been retired for a few years but I've found aftermarket wires worked fine but weren't crimped properly on the spark plug end. If an engine was missing and a customer came in with a misfire and I noticed new plug wires I either used my scope or an ohm meter and checked the wires. They run around 1/2 scale depending on the length. Usually a wire on the plug end wasn't crimped properly.
I have a pair of plug wire pliers and cut off about 2 or 3 inches and used the same end but crimped it properly.
An independent can't get away with charging for new wires when they installed new wires them selves I charged shop time to check out and do the repair.
If you have a pair of plug wire pliers check and repair.

[Thor1993]

Rhandwor – Actually I had one wire end stay on the spark plug so I re-crimped it with needle nose pliers. I checked ohms and I was getting 5 but I can’t remember what scale I was on. I probably should have cut an inch off the wire like you do. After the compression test I went for a test ride and as usual it ran great for a few miles than terrible so I think the plug wire was OK after I fixed it.

[Schurkey]

We already know the exhaust manifold should be replaced. This is a priority.

First Guess: You're going to need a REAL scan tool to track down any remaining problem(s) after the manifold has been taken care of.

What will take weeks to discover by replacing parts will show up on the scan tool in ten minutes.








It is not possible to create a proper spark plug end crimp with a needle-nose pliers.

[rhandwor]

Its next to impossible to do a plug wire crimp with needle nose pliers.
http://www.ebay.com/ Search 370320134406 I have a couple of pair that look like this. They do both 7mm and 8mm plug wire. As suggested a good scan will help you find the problem. From past experience if your timing chain hasn't been replaced its ready for replacement at this time. Remember if you cut a short piece from the wire you have to skin off about 1/2 inch so the carbon core can be doubled over the wire under the terminal.

[Thor1993]

Hi Guys,
What does this scan tool look like?? Is it a hand held unit I can purchase or is it an expensive tool only a shop would have? In the old days in high school auto shop class we used to put problem cars on a big old Sun Scope and look at the screen to find problems but I haven't seen one of those in decades at a shop. Remember this truck is a 1993. All I have been doing is using a paper clip to read codes and now all I get is 12 12 12 which means no problems that the ECM can tell me. I should tell you I also have a 98 Astro Cargo van with a 4.3L. At the moment it is running fine but I believe for a 98 there are hand held scanners that can tell you a lot. If a scanner is something a home hobby mechanic can afford I would like to buy one that would work for both trucks.

I will order a new Dorman manifold today or tommorrow. I would like a GM one but I will freeze to death at the junk yard now.

Thanks for all the guidance, it is really appreciated.

Greg