Mechanics

98 CHEVY S10 IDLE PROBLEM

1998 Chevrolet Truck

I have a 98 Chevy S10, 177,000 miles, 2.2L 4-cyl. A few days ago it started idling at full throttle. It would drive OK in gear, but it idled at full speed.

The check engine light came on, and I have 2 error codes:

P0336-- Crankshaft Position Sensor A Circuit Range/Performance

P0507--Idle Control System RPM Higher Than Expected

I found a busted vacuum hose and replaced it. Now the engine lopes excessively at idle, but doesn't race like before. Any hints at this point would be greatly appreciated.
Avatar
Young
March 2, 2007.



Sounds like the Crank Position Sensor might be going out

Tiny
Jack42
Mar 2, 2007.
I was mistaken. It was a camshaft position error, which was probably triggered by a misfire during the rough idle.

I replaced the IAC valve and cleaned out the throttle body. I also replaced a blown vacuum hose. Still not fixed -- now what?

Thanks.

Tiny
Young
Mar 9, 2007.
I still have the idle problem, with error code P0507. Every time I clear the code, it comes back on within a few minutes.

The problem is getting worse. The engine is revving up and down at all driving speeds now. It never threatens to stall, just throttles up and down. It's very rhythmic. For example, at idle it goes from about 800 rpm to 2000 rpm and back again every one or two seconds. It's still driveable, but fuel economy is in the toilet.

Occasionally the problem disappears for a little while, then it's back and the same code gets set.

Here's what I've done so far: 1. Replaced busted vacuum hose

2. Replaced IAC with a used one

3. Took the truck to a professional shop for diagnosis -- they said replace the IAC with a new one.

4. Replaced IAC with a new one

5. Replaced the throttle position sensor

6. Replaced the engine coolant temperature sensor

7. Slammed the hood in frustration.

Anyone want to buy a Chevy S-10? It needs work, but I don't know what!

Any help would be appreciated -- I'm losing what hairs I have left.

Thanks in advance.

Tiny
Young
Apr 5, 2007.
Hey, I am having similar problems! The idle is very irradic, it will go from 700 up to 2000. When it dose this and I shut of the engine, wait like 10 seconds and restart, (most of the time) it will run fine for a while, sometimes a few hours, sometimes a few days, there is no telling. I have replaced most of the things that you have replaced and have had no results. Once in a while when I start it it will just die, and it will take me a few tries to get it going. Another thing that I have noticed, is that the fuel pump relay (located in the glove box) will start clicking like crazy and the dash lights up like a christmas tree. If you have any luck I would appreciate it if you could give me a shout! Thanx

Tiny
Nunya
May 12, 2007.
It turns out it was still a vacuum leak in spite of my careful replacement of the busted vacuum hose. The EGR valve tube was broken where it enters the intake manifold. The break was on the inside, and difficult to see. It would move around, sometimes sealing (idle somewhat normal) but mostly leaking (idle irratic). This was the second garage I took it to, and they had the benefit of all my mistakes to aid in the diagnosis, but they admitted it still took a while to figure it out.

If your problem is with a 4 cyl. Chevy S10, look at the insulated tube that goes from the firewall to the intake manifold on top of the engine. If it wiggles it needs to be replaced.

I have a nice Suburban, and a Mustang convertilble to drive, but I missed my truck, and I'm glad to have it back on the road!

Tiny
Young
May 14, 2007.