94 Jimmy no power on highway

[shanes76]

my 94 Jimmy 4.3 vortec vin"W" has some issues, after it warms up it has a miss, changed plugs and wires, checked cap and button- cleaned them, recleaned EGR, recleaned IAC, just seems to have a miss while aitting at a stop light or in park, dont miss when taking off, also when your on the highway it seems like it dont have power cause you have to floor it to get 65 up hills but on smooth ground it goes, I just got my fuel filter off and was looking at it, on one end its open which is where the line from the tank was on the other end its not open but it looks like someone punched a a small hole in it- maybe 3/16 in diamater- could this be the reason for no power- not getting enough fuel? I also checked for play in the distributor and everything seemed fine there

[MT-2500]

Originally Posted by shanes76

my 94 Jimmy 4.3 vortec vin"W" has some issues, after it warms up it has a miss, changed plugs and wires, checked cap and button- cleaned them, recleaned EGR, recleaned IAC, just seems to have a miss while aitting at a stop light or in park, dont miss when taking off, also when your on the highway it seems like it dont have power cause you have to floor it to get 65 up hills but on smooth ground it goes, I just got my fuel filter off and was looking at it, on one end its open which is where the line from the tank was on the other end its not open but it looks like someone punched a a small hole in it- maybe 3/16 in diamater- could this be the reason for no power- not getting enough fuel? I also checked for play in the distributor and everything seemed fine there

REPLACE THE FILTER AND RUN A FUEL PRESSURE TEST.
Post back pressure readings.

Other things to tes is engine vacumn at idle and at 2K.
Post back vacumn readings.

Any codes or check engine lights?
If a engine miss find out what cylinder is missing and check for good spark to it and check compression reading.

Good Ac delco plugs?
Has base timing been set?

[shanes76]

Im going to get the filter this morning, only SES light is 43(knock sensor) put new ac delco plugs in and duralast wires, cleaned the cap and rotor yesterday, the tabs on the cap were a white color, button looked new and didnt have the white stuff on it, not sure if base timing has been set or not, I havent had it that long and the guy I got it from didnt seem to be firing on all cylinders either, but anyway, they had put on a new map sensor and never cleared the codes, and also the first time I put it in gear, I put my foot on the brake and pull down to like to R and it will do a short rev, but after that it dont do it again, almost like the IAC valve is moving slowly or something

[shanes76]

what should the timing be set at? I know to unplug the wire under the carpet on the passenger side, and also MT- since it like like the IAC is not moving freely, can I take it out, leave it plugged in, turn the key to on and push the throttle to see how its moving? Or does it have to be running? I seen a thread of how to take one apart and clean it, I tried that on an old one but it wouldnt come apart.

[MT-2500]

Originally Posted by shanes76

what should the timing be set at? I know to unplug the wire under the carpet on the passenger side, and also MT- since it like like the IAC is not moving freely, can I take it out, leave it plugged in, turn the key to on and push the throttle to see how its moving? Or does it have to be running? I seen a thread of how to take one apart and clean it, I tried that on an old one but it wouldnt come apart.

Base timing is set at 0 degrees TDC.

Check that fuel pressure.
Does the IAC control idle RPM.
What is idle rpm in gear and out of gear?

[shanes76]

I had the battery disconnected while doing the fuel filter and I also checked my IAC valve(one thats on the truck) and if I wiggle it back and forth like the thread said it does move in and out, so I lubed up the shaft on it to allow it to operate easier just in case, I dont know what the RPM's are since I dont have a tach. SO I guess Im off to do some driving and let everything reset to see what I got now

[shanes76]

well really no change in anything, still got the miss, it only misses after it warms up. and still seems to have no power on the highway- and I mean to go 65 mph, just like it has nothing

[Darren509]

Fuel pressure test.....

[shanes76]

thats the next thing, if it has low pressure would it still start good ? or would it be failing after running a few minutes

[shanes76]

I havent checked my pressure yet, but I have also noticed if Im holding a steady speed about 20-25 mph you can feel something like a surging, just like you are giving it gas then less gas and it just repeats, but dont notice it at high speeds, and when I get to 55mph in OD it seems to vibrate or something then at 60 it stopsand is smooth, think the vibration could be the motor mount that is broke?

[MT-2500]

Confirm good fuel pressure.
Put a gauge on it and drive 30 minutes or more and confirm good fuel pressure at all times from start up to 30-45 minutes of driving.
If engine is missing fix miss.
Vibration at around 60 MPH points to bad tire/bent wheel or mud in tire or out of balance.
Post back fuel pressure readings.

[shanes76]

MT I dont think the engine is really missing, it has been surging while holding at a slow steady speed Im hoping it is my regulator and not the fuel pump, I just have to get to the store to get the pressure tester, I have already replaced the return lines

[MT-2500]

Originally Posted by shanes76

MT I dont think the engine is really missing, it has been surging while holding at a slow steady speed Im hoping it is my regulator and not the fuel pump, I just have to get to the store to get the pressure tester, I have already replaced the return lines

Low fuel pressure will cause engine miss.
First thing Confirm good fuel pressure.
Post back all fuel pressure readings.

[shanes76]

think it might be fixed MT- got the knock sensor in and checked base timing, we had to move the dist. about 1/2 to 5/8 inch to get it in time and I believe the miss is gone now I just gotta get'er on the highway and try it out- thanx for all the help and I will let you know how it does.

[MT-2500]

Originally Posted by shanes76

think it might be fixed MT- got the knock sensor in and checked base timing, we had to move the dist. about 1/2 to 5/8 inch to get it in time and I believe the miss is gone now I just gotta get'er on the highway and try it out- thanx for all the help and I will let you know how it does.

You are welcome.
Thanks for posting back how it is going.
Let us lnow if ALL IS WELL.