you have any fuel washing in your vacuum harness assembly on top of the throttle body?

I kind of had the same type of performance issue with a random buck and power loss it ended up my Fuel pressure regulator was bad. Gas was leaking through the FPR and being pulled into the tb vacuum harness and would eventually make its way through the PCV and cause the misfire.

 

you have any fuel washing in your vacuum harness assembly on top of the throttle body?

I kind of had the same type of performance issue with a random buck and power loss it ended up my Fuel pressure regulator was bad. Gas was leaking through the FPR and being pulled into the tb vacuum harness and would eventually make its way through the PCV and cause the misfire.

How do I go about checking for the fuel getting into the vacuum harness? Is a FPR difficult to change on a 2.2?

Thanks for the help.

 

Do you smell fuel vapors in any of the vacuum lines? How about the oil? Pull the dipstick and take a sniff.

 

Do you smell fuel vapors in any of the vacuum lines? How about the oil? Pull the dipstick and take a sniff.

I'm gonna go out and check now, although I have a sinus infection and can't smell to much right now...

 

Fuel vapors might help you "flow", but I wouldn't suggest it as a regular thing. ROFL!

 

Fuel vapors might help you "flow", but I wouldn't suggest it as a regular thing. ROFL!

Gotcha . Definitely not a regular thing.

Well, I confirmed I can smell gas. I took off the gas cap just to make sure.

No fuel fumes in the oil. I also pulled off the vacuum harness on top of the throttle body, no fuel fumes there. I started up the truck, fired up quickly as it normally does. While it was running I pulled off the vacuum line going to the top of the fuel presssure regulator, no fuel there either. Reved it up to about 3k and it held steady with no hesitation. No vacuum leaks, I listened everywhere I possibly could.

Checked my codes and still getting Code 25...this will be an ongoing investigation and its driving me nuts. I'm on my third IAT sensor and I cannot believe it would be 3 in a row gone bad...

Any further ideas would be helpful...Thanks again..

 

so your code 25 has gone away in the past or no?
Do you have an aftermarket intake?


how does your IAC valve look? is it and/or your TB all gunked up with carbon/dirt?

 

Ok, any chance the IAT is unplugged or not plugged in all the way? Have you changed anything on the air intake system? Other than the air filter I mean..

Just a thought, check to make certain your cooling system is full, as well as checking your radiator cap. I think it's supposed to be 15 lbs pressure. Humor me on this question.. LOL

 

Parimeters..

Inlet Air Temperature Sensor signal showed an air temperature over 304° F after the engine has been running for 5 minutes and 20 seconds and the vehicle speed was greater than 15 MPH.

 

1995 S10 Ext. Cab LS 2.2L 5-speed 40,XXX original miles....

So here goes...I have an intermittent bucking issue. It keeps throwing the Check Engine Light- Code 25 - IAT sensor or circuit high temp indicated.

Sometimes it is runs perfectly fine and other times it starts bucking/surging no matter how far the gas pedal is pressed. It does not make a difference if the engine is hot or cold. It starts up fine very time and I can hear the fuel pump when I turn the key. I have reset the computer by pulling the fuse and also by disconnecting the negative battery cable but the check engine light normally comes on at highway speeds then goes out. But I still get the Code 25.

Here are the parts that have been changed within the past month or two:

Intake Temp Sensor - 3rd one, I doubt this is the problem.
Throttle Position Sensor - This fixed the CEL Code 22
EGR Valve - This fixed the CEL Code 32
Spark Plug Wires - AC Delco
Spark Plugs - AC Delco - Old spark plugs had the normal brown-grayish color on all cylinders according to Haynes manual. No oil or anything.
PCV Valve
Fuel Filter
Air Filter
Battery

One last question, would a clogged cat or fuel pump going bad cause intermittent issues like this? The whole thing is not making sense to me, so thats why your expertise is needed.

Like I said, I'm at my wits end. Not sure where to go from here. Your help is appreciated. Thanks in advance.

1.) change your fuel filter
2.) unhook your exhaust before the cat
3.) check wiring around the "High' side of the A/c for burns on the wiring harness going to the IAT.
4.) disconnect IAT and wrap in tin-foil indside a tissue tube:
in other words, isolate the IAT from the engine compartment.
5.) check wiring to IAT.

 

To ratrace2, mcdadcop, & chucky510; In the next couple of days I will check everything you mentioned and post my findings here....stay tuned and thanks again for the input.

 

so your code 25 has gone away in the past or no? Only if I reset the computer
Do you have an aftermarket intake? No
how does your IAC valve look? is it and/or your TB all gunked up with carbon/dirt? It was all gunked up. See the before and after pics of the IAC

Ok, any chance the IAT is unplugged or not plugged in all the way? It's plugged in
Have you changed anything on the air intake system? Other than the air filter I mean.. Everything on the truck is completely stock...looks like the cat has been changed
Just a thought, check to make certain your cooling system is full, as well as checking your radiator cap. I think it's supposed to be 15 lbs pressure. Humor me on this question.. LOL Coolant is full with the orange stuff. Cap looked good...not sure how to check the pressure of it

1.) change your fuel filter changed back in January
2.) unhook your exhaust before the cat didn't get a chance to do this
3.) check wiring around the "High' side of the A/c for burns on the wiring harness going to the IAT. wiring looks good everywhere
4.) disconnect IAT and wrap in tin-foil indside a tissue tube:
in other words, isolate the IAT from the engine compartment. gonna try this soon
5.) check wiring to IAT. wiring looks good

Here are the other checks I did:

1.) IAC Valve Cleaned
2.) IAC Valve resistance checked
A-B=49.5 C-D=49.6 Tolerance is 40-80 ohms according to
Haynes
3.) Throttle body and all vacuum ports throughly cleaned with throttle
body cleaner
4.) Cleaned MAP Sensor port on intake
5.) Checked reference voltage to MAP = 5.01 volts
6.) Checked Coil Pack Secondary Resistance
2-3 = 5,420 ohms
1-4 = 5,550 ohms
Haynes manual says 5,000 - 10,000 ohms is good
7.) Checked resistance on coolant temp sensor
Cold 5,500 ohms Haynes says 2,200 to 5,700
Hot 300 ohms Haynes says 170 to 450 ohms
Checked reference voltage to temp sensor=5 volts
8.) Checked crankshaft sensor resistance 910 ohms Haynes says 800-
1200 ohms
9.) Checked IAT reference voltage 5.01 volts
2600 ohms at 50 degrees which is good according to Haynes
10.) Coolant level is full with the dexcool orange
11.) radiator cap seemed to be fine
12.) Checked and shook every piece of wire I could get my hands on while
it was running. No misses or stumbles. Everything looked to be in
great shape wiring wise.

I started it and let it run for about 30 minutes. Prior to starting, I cleared the code 25. I still have to take it for a test drive to see how it runs. Ran nice and steady at idle but, every once in a while had a very quick and slight miss. I am wondering if the coil pack secondary resistance being so low means my coil packs are on there way out...

I will post once I take it for a drive to see how things work out...

 

good luck man.

 

Hell yes man. You have done your math alright! Good on you bud!

 

Hell yes man. You have done your math alright! Good on you bud!

i tried to check as much as i could while i had my multimeter in hand. i have been in the aviation field for 19 years, so needless to say i am extremely anal when its comes to testing and troubleshooting. just hoping and being patient trying to solve my issue.

thanks for the help n8rsk8r

 

Before you throw any more parts at it, you need to fix the iat problem. Check for a short to ground in the wires between the iat and pcm. This will likely fix your bucking issue.

 

Before you throw any more parts at it, you need to fix the iat problem. Check for a short to ground in the wires between the iat and pcm. This will likely fix your bucking issue.

Hey Hoosier. Here is what I did concerning the IAT problem.

1.) I removed the PCM and found the tan wire on the wiring harness that goes to the IAT sensor.
2.) I checked the entire length of the tan wire from the PCM to the IAT with my multimeter. I connected the multimeter to both ends of the tan wire and shook the he!! out of it along the entire length of the tan wire. No breaks in the tan wire. So the tan wire is good. The only other thing it could be (as far as I can tell) is an intermittent short in the ground wire.
3.) I spliced in a new ground wire from the IAT sensor connector to a good chassis ground.
4.) I made sure any codes were cleared. Started the truck and let it run for a few minutes. I tapped the PCM with my fingers over the entire PCM to see if maybe there were any issues with it. No misses, stumbles or check engine light.

Getting ready to take it for a test drive in a few minutes to see if this worked...

 

Well, I took it out for about a 15 mile drive. I ran the pi$$ out of it. Full throttle, have throttle, feathering the throttle, and amazingly enough, there were no bucking or missing issues, no check engine light or codes thrown. Ran like a new truck again.

However, the true test will be on my 40 mile round trip to work tomorrow. If that drive is uneventful, than I know for a fact the ground wire was bad and I need to hunt it down, even though I ran a new ground.

Keeping my fingers crossed...

 

may the force be with you..

 

I do believe the force was with me today

I drove to and from work today, a little over 40 miles or so, and to much surprise, no bucking, no missing, no nothing except a good running truck (knock on wood)

I guess relocating the ground wire going to the IAT sensor fixed the problem.

Hopefully this issue is now closed.

My Thanks to everyone who helped me out on this one.

Its nice to have an S10 support group...

 

LOL at times we need one.. every one of us!

I like the way this was handled, have family members who are aviation wiring wizards. Makes sense knowing that now, how you busted out the equipment and went to work. Good stuff. I started a thread a bit ago about those grounding kits. I am glad to see that the grounding issue is an actual issue and will get mine taken care of very soon.

 

LOL at times we need one.. every one of us!

I like the way this was handled, have family members who are aviation wiring wizards. Makes sense knowing that now, how you busted out the equipment and went to work. Good stuff. I started a thread a bit ago about those grounding kits. I am glad to see that the grounding issue is an actual issue and will get mine taken care of very soon.

Thank you and I look forward to being an active member of this forum

 

congrats on the fix !