90 r1500 subruban acting up.... Help

[Vbb199]

And 4.38 WOT?

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[Arkansas_V8]

Does .63 sound like a reasonable voltage with the throttle plate closed?

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Believe it should be closer to .50. Should be smooth all the way to full throttle.

 

[Vbb199]

Was smooth all the way, like I said, at WOT it was 4.38 or whatever.

Idk if that's "close" to 5v

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[Vbb199]

Looked into Dist.
Center coil tower was missing all together....
Replaced it with a good old one just to try...
Still nothing... Won't stay running, bogs down on idle when throttle is pressed.

Tried another EGR earlier just for ***** and giggles because I had a good one on shelf.... Still no change.

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[Vbb199]

Did we try the TPS already?


It only has so many sensors. Its basic.

You are getting fuel, good spark, air.

Why cant we pull codes?

I apologize, you asked about codes.... The codes are gone now. I just had a engine light very briefly while I was driving it... By the time I was home, it was gone.

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[gmbellew]

I apologize, you asked about codes.... The codes are gone now. I just had a engine light very briefly while I was driving it... By the time I was home, it was gone.

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i think it stores codes for a certain number of starts after the light goes away. i would still try to pull the codes.

 

[Vbb199]

i think it stores codes for a certain number of starts after the light goes away. i would still try to pull the codes.

All I got was code 12

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[Vbb199]

To sum all this bs up for any new viewers, this is what all I've done today:

I checked EGR, PCV, new spark plugs, replaced cap with a good used one, checked TPS, and sprayed ether for vacuum leaks, replaced coolant temp sensor with a new one.
Tried bypassing EGR also....
No luck.. Won't stay running. Dies almost immediately upon firing it up unless I keep giving it gas.

Even tried a simple computer reset by unplugging battery..... No luck.


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[C10MixMaster]

I did plugs 1 wire at a time, OEM plugs, nothing fancy. However to be sure, I did check plug order, it's all the same. I can see the fuel spraying like it should In time with the motor still, but for sure, the problem has gotten worse, I can only assume because it's cooled down now. It was acting pretty much the same way earlier when I was driving it.. Barely able to run.

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were the plugs wett when you replaced them ? if so you might have a weak spark and an ignition problem. if not then you have a fuel ratio problem. your injectors may be spraying but not enough. a fuel filter is cheep and easy and may cure this (from experience). If you can check the pressure that would eliminate filter, regulator ,pump, return line etc. another thing to check is the vacuum line to the map sensor.

 

[Vbb199]

were the plugs wett when you replaced them ? if so you might have a weak spark and an ignition problem. if not then you have a fuel ratio problem. your injectors may be spraying but not enough. a fuel filter is cheep and easy and may cure this (from experience). If you can check the pressure that would eliminate filter, regulator ,pump, return line etc. another thing to check is the vacuum line to the map sensor.

I would say I have a pressure gauge, but I'm sad to admit I got a little slammed one night and hooked it up to a truck with 60 lbs of pressure and killed the poor thing, so I don't really know what kinds pressure I'm getting to be honest.



Plugs weren't wet when I hooked them up

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[Vbb199]

I would say I have a pressure gauge, but I'm sad to admit I got a little slammed one night and hooked it up to a truck with 60 lbs of pressure and killed the poor thing, so I don't really know what kinds pressure I'm getting to be honest.



Plugs weren't wet when I hooked them up

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Vacuum like to the MAP sensor seemed alright, but I do have a good map sensor on the shelf from my k5 I took apart I can try.

A friend of mine that runs nothing but OBS trucks suggested the MAP sensor

Sound legit?

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[C10MixMaster]

yes a map sensor or vacuum line to will kill any drive ability.

i would expect a code from a bad map though

 

[Vbb199]

yes a map sensor or vacuum line to will kill any drive ability.

i would expect a code from a bad map though

I'll swap MAP and try it out tomorrow

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[1987 GMC Jimmy]

This all happened really fast, but the best thing to do is remind yourself how simple it is and take a step back. Air, fuel, and spark. Have you looked at the spray pattern when it does start for a minute? You might have to get someone to stay on it for you, but if the pattern’s weak, or one injector’s dead, it’ll run bad. Just listening to the fuel pump is a good start because you can hear when it’s dying or not getting enough juice.

Your TPS voltage is fine. I’ve never been able to do better that .59, and that’s after boring the holes out and pivoting the sensor. CTS would cause a nasty rich condition and possible bad running, but I don’t believe it would to the extent you describe. MAP losing vacuum would cause it to run really really bad, but you can try to unplug the sensor and let it defer to the TPS exclusively. That’ll be a good clue, but you said you have a spare. I wouldn’t worry with O2 and EGR/solenoid at idle. The IACV is the only one left, but I’d personally save that for later.

Sounds like the cheap and easy parts of your ignition system are good, but I would test the ignition module, coil, and pickup coil. I’ll attach a test for the latter two, but you’ll have to take the ICM out to have it tested at Autozone or O’Reilly. You can also get a test light probe and hover it over the coil pin and see if you’re getting good spark there and then over the cap pins to see if good spark is leaving the distributor. That assumes that plugs and wires are good to go.

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[Vbb199]

This all happened really fast, but the best thing to do is remind yourself how simple it is and take a step back. Air, fuel, and spark. Have you looked at the spray pattern when it does start for a minute? You might have to get someone to stay on it for you, but if the pattern’s weak, or one injector’s dead, it’ll run bad. Just listening to the fuel pump is a good start because you can hear when it’s dying or not getting enough juice.

Your TPS voltage is fine. I’ve never been able to do better that .59, and that’s after boring the holes out and pivoting the sensor. CTS would cause a nasty rich condition and possible bad running, but I don’t believe it would to the extent you describe. MAP losing vacuum would cause it to run really really bad, but you can try to unplug the sensor and let it defer to the TPS exclusively. That’ll be a good clue, but you said you have a spare. I wouldn’t worry with O2 and EGR/solenoid at idle. The IACV is the only one left, but I’d personally save that for later.

Sounds like the cheap and easy parts of your ignition system are good, but I would test the ignition module, coil, and pickup coil. I’ll attach a test for the latter two, but you’ll have to take the ICM out to have it tested at Autozone or O’Reilly. You can also get a test light probe and hover it over the coil pin and see if you’re getting good spark there and then over the cap pins to see if good spark is leaving the distributor. That assumes that plugs and wires are good to go.

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It sprays good on both ports... No issues there, but like I said, I can't exactly check pressure until I get a better gauge, which isn't a huge issue, just need to make it up there....
Cousin stopped by and I had him keep it running for me, timing is good, fuel spray is good.. No issues there... Haven't listening to the fuel pump, but I'm thinking that's what's next tomorrow....

What would it run like without a MAP and just TPS?


A friend of mine suggested the pickup coil, module, and coil itself. I have all good spares of that as well I can try.
I suppose could test those things....


My family laughs at me for being weird and sensitive to noises the truck makes....
But yesterday, I swear, the truck was idling different, and the acceleration sounded different.... I knew something was up with my old truck... Sure enough today... She acted up

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