egr valve ? 94 full size

[starfiresx]

Hello all, found this site looking for info on EGR valves.

I have been having this like hesitation/missing problem on my 94 k1500. taking off from a stop it hesitates like it is missing. it started off just a little bit. and only when the engine was warm/ running temp. not at all when cold. but in the last week. it has started to be most of the time, as the engine is reaching running temp. when it is cold and in the cold start loop. it runs great. but all down hill from there.

Changed the
O2 sensor
Engine temp sensor
swapped out the MAP senor and TPS sensor
new Distributor, cap and rotor
plugs
wires good quality, are only a year old.
new filter
new TBI base gasket
checked fuel pressure right at 13 psi
injectors are shooting fine
cut the cat off. thought it might be plugged.
checked all the vacuum lines
checked the timing right on before and after the distributor swap.

No codes.
No SES light. till I check the timing. then reset by disconnecting the battery.

now onto the EGR valve. I was told to try to disconnect it, and plug the port on the TBI. still the same.

so I took a vacuum pump with a gauge to my egr valve and it will not hold vacuum. should it? I believe so!

I am guessing it is bad.

also I put a vacuum gauge on the hose after the egr solenoid. and nothing until I move the throttle. then it only moves the gauge for a second and goes back to zero. is this right?

If I continue revving the engine higher it will give shorts blasts of vacuum. on and off.

If the diaphragm is bad, would this let in air and be causing my problem?

think this would be some of my problem with my hesitation/miss like feeling that I have?

I will be replacing the EGR valve ASAP.

any advice is appreciated. thanks Joe

[Elbert]

Originally Posted by starfiresx

Hello all, found this site looking for info on EGR valves.

I have been having this like hesitation/missing problem on my 94 k1500. taking off from a stop it hesitates like it is missing. it started off just a little bit. and only when the engine was warm/ running temp. not at all when cold. but in the last week. it has started to be most of the time, as the engine is reaching running temp. when it is cold and in the cold start loop. it runs great. but all down hill from there.

Changed the
O2 sensor
Engine temp sensor
swapped out the MAP senor and TPS sensor
new Distributor, cap and rotor
plugs
wires good quality, are only a year old.
new filter
new TBI base gasket
checked fuel pressure right at 13 psi
injectors are shooting fine
cut the cat off. thought it might be plugged.
checked all the vacuum lines
checked the timing right on before and after the distributor swap.

No codes.
No SES light. till I check the timing. then reset by disconnecting the battery.

now onto the EGR valve. I was told to try to disconnect it, and plug the port on the TBI. still the same.

so I took a vacuum pump with a gauge to my egr valve and it will not hold vacuum. should it? I believe so!

I am guessing it is bad.

also I put a vacuum gauge on the hose after the egr solenoid. and nothing until I move the throttle. then it only moves the gauge for a second and goes back to zero. is this right?

If I continue revving the engine higher it will give shorts blasts of vacuum. on and off.

If the diaphragm is bad, would this let in air and be causing my problem?

think this would be some of my problem with my hesitation/miss like feeling that I have?

I will be replacing the EGR valve ASAP.

any advice is appreciated. thanks Joe

I had a problem like this on my 92K1500, I ended up replacing the knock sensor, its down by the starter. Real easy to swap out.

[Bob B]

Originally Posted by starfiresx

Hello all, found this site looking for info on EGR valves.

I have been having this like hesitation/missing problem on my 94 k1500.
now onto the EGR valve. I was told to try to disconnect it, and plug the port on the TBI. still the same.

so I took a vacuum pump with a gauge to my egr valve and it will not hold vacuum. should it? I believe so!

I am guessing it is bad.


I will be replacing the EGR valve ASAP.

any advice is appreciated. thanks Joe

------------------------------------------------------
Hi Joe,
I don't think the failure to hold vacuum is bad.
My wife's car a 91 Caddy STS, did the same thing so I bought one from the dealer.
The new one was the same, Therefor I didn't install it and I asked a knowledgeable mechanic about it. He said they use exhaust pressure plus vacuum to open them currently. The original ones a number of years ago did just hold vacuum and you could suck them open.
Luckily the dealer parts counter actually took it back and no restocking fee either.

[starfiresx]

well I pulled the egr valve off the engine and did the vacuum test again. it worked fine this time. let it stand with the pump attached to it and it held vacuum. so on the truck it would not hold. maybe I had the engine running at the time do doing this test. can't remember. but must have.

I recreated this with the vacuum pump holding vacuum on the valve,and used an air hose and gave it some air in the round orifice and the valve closed.

so I cleaned it all up and replaced with a new gasket.

with my finger I can move the valve and it will slow and then kill the engine.
so this must be OK! I guess?

later Joe

[fatmacsumo]

you need to change the egr a lot of times people underestimate this part if that dont work you have an internal vacumn leak possible pcv valve or intake manifold also ck your brake booster let me know

[starfiresx]

Well no leak at the brake booster, it holds a vacuum. pvc seems to be working correctly. I took a can of starting fluid and sprayed it all over the place. nothing! but yesterday. the first time I had to drive this truck in awhile. I drove it about 6 miles and it was running very sluggish. turned it off came back out and it would not start right up. got it running and it was running very rough. I moved the distributor, advancing the timing and it runs much better. it is like at four BDTC now. but still has this miss/hesitation. could the timing chain be going/stretching out? or the ELECTRONIC SPARK CONTROL MODULE be giving me this problem.

last night I drove the truck home from work and it was fine till I had to get off the highway. then taking off from a light it was back the hesitation. but the truck will do 80 mph just fine.

in the winter I use this truck to push snow. do you think there is a lot off stress on the chain because of this? I will pull the cap of the distributor and rotate the engine clock wise and then counter clockwise and see if there is a lot of slop in the chain.

thanks Joe

[starfiresx]

Well, I think I may have the problem licked. I took off the egr valve and put in it's place a block off plate and plugged the TBI vacuum port. let it get up to temp and took her for a ride. all like before the problem ever arose.

so now I need to know. can I leave it like this? or should I buy a new valve and or egr solenoid?
I know what the egr does and how it works. but here in Michigan we do not test at the pipe any more.

what do you guys think.
also no SES light as of yet.

thanks Joe

[fatmacsumo]

if you are not having a loss of power or no serv eng light you will be fine. just remember if you do have a serv eng light on when something else happens you want know

[starfiresx]

well, this thing is still driving me crazy!!!

sealed up a crack in the manifold with fire seal 2000. stuff works great.

the SES light came on, ran the code. 32

I replaced the EGR valve and it still acts up.
put the block off plate back on and now it still acts up.
I check the TPS sensor found a bad spot. replaced with new one. it is much crisper off the line. but still has the hesitation.

I am starting to think it may be a bad torque converter solenoid. trying to lock up the converter. or the fuel pump is starting to go. I did check the pump when it was cold before right at 13 psi. I am going to put the fuel pressure gauge back on and run a longer line and tape it to the window and see what I come up with.

is there a way to check the tbi pressure regulator?
if the pump is going out? would the O2 sensor pick up on it and give a code 44?

is there a way to disconnect this solenoid to test my theory?

Joe

[2000CAYukon]

Has the timing chain every been replaced? Does the timing jump around when you check the timing?

I have a 90 K1500 with 116K miles. Original owner with the truck. I recently checked the timing and the timing was jumping so I swapped out the chain and gears. I was suprized by how much slack was in the chain.

The other thing you should check is the heat riser in the air cleaner. It is heat activated and it will go bad over time (mine was). When it goes bad, hot air is going into the TBI instead of colder outside air. If you take off the air cleaner lid when the engine is hot, look to see if the heat riser is closed or open. I rigged mine to always allow cold air in since I live in a warm climate.

//2000CAYukon

[starfiresx]

the heat riser is operating correctly. thanks for the info.

also I have been told by a GM person that GM started using better chains in the truck in 92. also I only had like 3 or 4 degrees of slop in the chain. seems OK?

today I replaced the fuel regulator, no change. pulled the old one apart, looked good.
also I placed my T in the fuel line and ran a hose up the window and taped it to it. took the tuck for a run, and made sure that everything was all warmed up. the pump keeps right up. no loss of pressure. 13 PSI

took the plugs out and did a compression test. all the cylinders came in a little high. at 180 PSI. it should be like 150 PSI. so the book says that the combustion chambers are probably coated with carbon deposits.

how can I try to get rid of this if this is the case. anything at the parts store I can try. or any old time remedy?

thanks Joe

[2000CAYukon]

Originally Posted by starfiresx

also I have been told by a GM person that GM started using better chains in the truck in 92. also I only had like 3 or 4 degrees of slop in the chain. seems OK?

That should be OK. On my 90, when I was checking the timing, the mark would jump 20 degress sometimes.

took the plugs out and did a compression test. all the cylinders came in a little high. at 180 PSI. it should be like 150 PSI. so the book says that the combustion chambers are probably coated with carbon deposits.

how can I try to get rid of this if this is the case. anything at the parts store I can try. or any old time remedy?

thanks Joe

I have heard of Seafoam but no experince with it.

Is the IAC working properly? When the TPS changes it is suppose to pull back (high count on a scan tool).

Do you have access to a scan tool or WinALDL to see if your knock count is high (bad knock sensor)?

Did you plug the vacuum hose to the EGR solenoid? Mine would not hold a vacuum so I replaced it.

Good luck!

//2000CAYukon

[Crasen]

I have known several people who have used seafoam and they all swear by it. I have not used it yet myself plan I do plan on it shortly. I have seen it at autozone for about 6 dollars a can. I doubt it would be a torque converter clutch, these ussually cause a rather harsh bucking, and sometimes stalling

[fatmacsumo]

did you change your egr solonoid this is also 32 code related that is what is located at the other end of the vacumn line going to your egr.

[self-made-mechanic]

Just subscribed to this forum. Seems that I've got the same hesitation in my 1993 K1500 5.7 liter. Problem NOT solved by (1) new EGR (2) new O2 (3) new plugs (4) new fuel and air filter. I will be replacing the wires and cap/rotor this weekend.
Suggestions from this forum mention the following:
- fuel pressure regulator
- mass airflow sensor
- cleaning throttle body
- leak in intake manifold
- fuel pump
- knock sensor

I did buy a fuel pump but not looking forward in dropping the tank.

The symptoms of hesitation occur after warm-up, @ 1500 RPM and light pressure on the gas pedal ( I have a 5-speed manual), and runs better under more throttle, higher RPM. Gas milage has declined. Will keep posted.