Jimmy run worse after air intake temp replaced

[mckenzi]

I have a 1995 GMC Jimmy s15, 102,000 miles, just got it last month, I have noticed it missing since purchased from private owner and replaced the spark plugs and wires and it was slightly better but still burns gas like crazy. I took it to Car Doc their computer revealed it needed a replacement intake air temperature wire connector for $48.00. Very short drive home revealed smoother performance and a slight miss still at idle ands at park and drive when held by emergency brake. The next morning drove 25 miles in the rain, highway ok, every stoplight it stumbles and misses so bad you think it will cut off. I am almost afraid to take it back to these people, any suggestions? I have spent much money on this vehicle this month, U joints, lower ball joints, idle arm, master cylinder....I'm thinking it is the truck from hell now. Thanks

[94 Jimmy]

I have a 94 Jimmy, gee funny, same as my login. Believe me I've been through it too. My general advise is read up on your truck and get aquainted with its problems and fixes, most arn't to difficult. I spent almost $1000 at a mechanic just to have him shrug and say "Well, I just don't know".
I did a Google search on 94 Jimmy Idle Problems and within 5 minutes learned about the CPI, Central Port Injector. It's inside the intake manifold and has a tendency to leak. This adds fuel to one side of the intake and adds extra gas to three cylinders, the O2 sensor reads the combined exhaust in the exhaust manifold and trys to lean out the mixture which leans out the other three cylinders. All in all not a good way to run an engine.
I don't know if the 95's have a CPI but if they do, you will be able to tell if you remove the intake manifold cover and the cross manifold valve in the center of the manifold. Use an inspection mirror to see if the manifold interior is clean on one side and dirty on the other. This indicates that fuel leaking from the CPI fuel regulator is washing the inside of the manifold and making you engine run like ____.
If this is your problem check EBay they have a lot of them for sale, some are modified to beef up the regulator diaphram to reduce the tendency to leak.
Hope this helps, as for the other things, it's just the age of the truck. Remember it's 10 years old with 100,000 miles, time for some maintenance. When you get it running check the shocks also, if they haven't been changed already it's time.
Good luck
94

[BlazerLT]

Originally Posted by mckenzi

I have a 1995 GMC Jimmy s15, 102,000 miles, just got it last month, I have noticed it missing since purchased from private owner and replaced the spark plugs and wires and it was slightly better but still burns gas like crazy. I took it to Car Doc their computer revealed it needed a replacement intake air temperature wire connector for $48.00. Very short drive home revealed smoother performance and a slight miss still at idle ands at park and drive when held by emergency brake. The next morning drove 25 miles in the rain, highway ok, every stoplight it stumbles and misses so bad you think it will cut off. I am almost afraid to take it back to these people, any suggestions? I have spent much money on this vehicle this month, U joints, lower ball joints, idle arm, master cylinder....I'm thinking it is the truck from hell now. Thanks

Check your CI injector by removing the top vortec plate, the top round IMTV valve and peering in with a flashlight and looking for washed spots (golden color) and pools of fuel and a strong smell of gas.

Also smell your engine oil for gas.

[94 Jimmy]

I have a 94 Jimmy, gee funny, same as my login. Believe me I've been through it too. My general advise is read up on your truck and get aquainted with its problems and fixes, most arn't to difficult. I spent almost $1000 at a mechanic just to have him shrug and say "Well, I just don't know".
I did a Google search on 94 Jimmy Idle Problems and within 5 minutes learned about the CPI, Central Port Injector. It's inside the intake manifold and has a tendency to leak. This adds fuel to one side of the intake and adds extra gas to three cylinders, the O2 sensor reads the combined exhaust in the exhaust manifold and trys to lean out the mixture which leans out the other three cylinders. All in all not a good way to run an engine.
I don't know if the 95's have a CPI but if they do, you will be able to tell if you remove the intake manifold cover and the cross manifold valve in the center of the manifold. Use an inspection mirror to see if the manifold interior is clean on one side and dirty on the other. This indicates that fuel leaking from the CPI fuel regulator is washing the inside of the manifold and making you engine run like ____.
If this is your problem check EBay they have a lot of them for sale, some are modified to beef up the regulator diaphram to reduce the tendency to leak.
Hope this helps, as for the other things, it's just the age of the truck. Remember it's 10 years old with 100,000 miles, time for some maintenance. When you get it running check the shocks also, if they haven't been changed already it's time.
Good luck
94

[BlazerLT]

Yip, 1995's came with it.

Remove the vortec name plate and the imtv valve and have a quick peek.

[XtremeXP]

I have a 95 jimmy and your two main problems is carbon getting stuck in the EGR valve and the CPI unit like everyone is talking about. More than likely it's the CPI. I picked one up at a local parts store for a liitle over $200.00 over a year ago. Installed myself and really wasn't hard to put on. It's been running good ever since then.

[BlazerLT]

Yip, it causes the carbon problem which plugs open the EGR.

When you fix the CPI injector, the carbon blockage might occure a couple times after as it clears itself, but then it will be gone for good.

[mckenzi]

Ref the 1995 Jimmy Intake air temp / after consulting with Car Doc again, the mechanic said he did not know how long the wires for the intake air temp valve had been disconnected and this may have caused carbon build up. He suggested I drive and see if it will blow out and then bring it back in a couple days if not. I did drive it, scary at first, it would actually shudder at every traffic light, out on the highway it must have blown something out, twenty minutes later no more shudder, almost smooth. I will check out that CPI and I did already change the shocks, PCV (elbow fell apart and needed now one) and this had made a difference in gas consumption already. thanks again

[BlazerLT]

Replace the PCV valve also.

Check the CPI, chances are it still needs to be replaced.

[mckenzi]

Well I replaced the PCV valve and hose, because it fell apart and cleaned the Intake Air Temp Valve and followed the steps to make it learn idle and drive again and it is running much better and the gas mileage has slightly improved. I could not get the top off the vortec cover, someone has stripped the screws, will work on that soon as I get the correct ones to do this with. Thanks again