350 tbi problem???

[JOHN MEADOWS]

i haven't found a wire that would go to that knock sensor. what does the plug look like. I hate having to find and fix others mistakes. This has been nothing but a headache since i got he truck trying to track down things. A big thanks to you guys for helping me!!

 

[1987 GMC Jimmy]

What I’m saying is you may have to run a new wire straight from the ESC module if you can’t find the original wire.

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[4WDKC]

isnt it laying on the frame in that in the pic?

 

[Blue Ox]

I don't work with engines with ignition systems very often, but wouldn't a knock sensor be on the head or near the block deck? That really looks like a crank position sensor sitting behind the damper like that.

Do we know the history of this truck? That could be a junkyard replacement engine from a later truck, cause you know, a small block is a small block.

 

[4WDKC]

I don't work with engines with ignition systems very often, but wouldn't a knock sensor be on the head or near the block deck? That really looks like a crank position sensor sitting behind the damper like that.

Do we know the history of this truck? That could be a junkyard replacement engine from a later truck, cause you know, a small block is a small block.

What engines are you working on that dont have ignition systems?

its in the water jacket in the block not far from oil pan in center of the block.

 

[disenough]

That looks like a plastic vortec timing chain cover. The knock sensor is above the back of the starter.

 

[Snoots]

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[Snoots]

Here's the Crank Sensor location...

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[Blue Ox]

Isn't that ^^^ what's in his picture?

You know, right behind the damper, under the radiator hose? Doesn't look like it's anywhere near the starter to me.

 

[JOHN MEADOWS]

Things I found out!! I took to a friend the said it is vortec motor with my tbi stuff on it. I got under it and did more looking and it does have a o2 sensor and it's hooked up. After it warms up now I have noticed that it wants to idle high since I did the iac reset. I'm lost on this thing and about to give up!!!!

 

[1987 GMC Jimmy]

If your IAC valve is settling where it’s supposed to, then you might have a vacuum leak. It could be a big one, a bunch of little ones, or a combination. Your engine’s vacuum is something you need to check with a gauge. @4WDKC is 100% correct on needing a scanner to diagnose any sensor related issues. Also make sure your throttle linkage isn’t binding.

 

[4WDKC]

With the vortec heads you need to either have it tuned or make the fuel pressure regulator adjustable to jeep it from leaning out on the higher rpm.

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[GTP51]

Had similar issues to you, replaced nearly everything and along the way learned a heap about my TBI and it’s little tricks.
Have you replaced the TPS . (Throttle position sensor )
Have you replaced the EGR
Mine turned out to be a combination of the electronics, TPS and IAC with the final issue being a cracked vac line to the charcoal canister right next to the insulator that the factory put on the line to prevent burn through on the exhaust manifold.
Hope that helps

 

[JOHN MEADOWS]

Not replaced the tps yet on this . Just hate to keep throwing parts at it and not know for sure. Ill check all the vac lines again to see what i can find out.

Who makes a obd1 scanner that wont break the bank?

 

[4WDKC]

Not replaced the tps yet on this . Just hate to keep throwing parts at it and not know for sure. Ill check all the vac lines again to see what i can find out.

Who makes a obd1 scanner that wont break the bank?

I bought a couple snap on mt2500 at a swap meetfor a good price, you can buy a cable from www.moates.net or http://www.gmsquarebody.com/threads/connecting-with-a-laptop-with-tuner-pro-rt-and-diy-cable.13194/


if you wan tto test the tps just disconnect it, the truck will operate in limp home mode and use predetermined values instead of the sensors.