my truck misses after I warm it up

[chevyaz]

I have a 1994 gmc truck with

Topic

[dreamer2355]

Welcome to the forums!

I would be looking at mechanical timing of the engine with that amount of miles.

Did you do a compression test to see what the numbers are?

You can also do a cylinder balance test as shown in this video by Eric to see if you can isolate a potential cylinder thats misfiring –

http://www.youtube.com/watch?v=bAOmUjAjNjE&feature=plcp

Testing the TPS is very easy. You just need a DVOM and sweep test it. To test the MAP sensor, you will need a hand held vacuum pump and again a DVOM. Wiring diagrams will be needed so you can probe the correct wires. However, i dont believe those 2 sensors are your issue.

[chevyaz]

Quoted From dreamer2355:

Welcome to the forums!

I would be looking at mechanical timing of the engine with that amount of miles.

Did you do a compression test to see what the numbers are?

You can also do a cylinder balance test as soon in this video by Eric to see if you can isolate a potential cylinder thats misfiring –

http://www.youtube.com/watch?v=bAOmUjAjNjE&feature=plcp

Testing the TPS is very easy. You just need a DVOM and sweep test it. To test the MAP sensor, you will need a hand held vacuum pump and again a DVOM. Wiring diagrams will be needed so you can probe the correct wires. However, i dont believe those 2 sensors are your issue.

I have not done a compression test on it so I will check that and the timing. As far as the sensors I figure the would throw a check engine light if they were bad. Not trying to sound dumb but what is DVOM stand for? Is that a volt meter? Thanks for your help!!

[dreamer2355]

DVOM = Digital Volt Ohm Meter.

And there are no stupid questions.

I would do a power balance test first before doing a compression test.

It would also be worth while using a vacuum gauge and seeing what your readings are.

[chevyaz]

Quoted From dreamer2355:

DVOM = Digital Volt Ohm Meter.

And there are no stupid questions.

I would do a power balance test first before doing a compression test.

It would also be worth while using a vacuum gauge and seeing what your readings are.

Can you suggest a video on how to check the vacuum on my truck,and the timing is something i”ve never done myself. Might have a shop do that. Still new to the fix it myself thing.

[dollman0]

Have you tried an injector service?
It may be as simple as injectors with buildup on them from ethanol. A gummed up hydraulic lifter can also give you idle issues from a tight valve and still drive good.

[dreamer2355]

A vacuum gauge reading should be a steady 18 to 22″.

Here is Eric’s video on compression testing –

http://www.youtube.com/watch?v=X_tbksFYhl4&feature=plcp

Again, start with the basics and easiest first and see if you can pin point it to a particular cylinder.

[EricTheCarGuy]

I would shelve condemning sensors for now as you pointed out if you don’t have a check engine light for one then you probably don’t have a problem there. I think it’s a good idea to check the basics as suggested especially for vacuum leaks at the intake gasket as GM intake gaskets are famous for leaking and causing idle and performance issues. Here is a video that can help you find those leaks if you have any.
http://www.youtube.com/watch?v=9CPqbaSgcok+

[Author]

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