injector problem???

[Ron A]

I have a 94 explorer sport with 150,000 on it. Hwy MPG are close to 21-22 mpg. Power is ok and everything seems to work fine until I pull a long grade after 4 or 5 hours of Hwy driving. Then the engine check light will turn on and off. It feels like it has a slight surge in rpms without changing throttle position. It will idle rough while it is doing this. I changed spark plugs and I had ash deposits on the #4 plug, the rest were normal. So I changed all the plugs since they had 40,000 on them and still had the same problem after 5 hours of operation. #4 plug was looked normal when I repulled and checked it. After the motor cools overnight the check engine light goes out and it takes another 4 to 5 hours of operation and then a steep grade to start the cycle all over again. Anyone have a suggestion on what might be wrong. BTW I did clean the MAF sensor. Thanks.

 

[MrShorty]

Run EEC-IV self-test (www.dalidesign.com/hbook/eectest.html) to see what codes were triggered when CEL came on. They should be stored and will be retrieved during the continuous memory portion of the test.

 

[Ron A]

I get three codes: 53 throttle position sensor out of range high : 56 MAF Sensor out of range high: 176 lean condition left side : Lean condition tells me I may have a fuel delivery problem and #4 is left side center, the plug that had ash deposits. This is in memory so what would cause it to only act up after 4 or 5 hours of operation, is this common for an injector that is soon to fail or just fouled ? Or is it possible that the MAF sensor failing could cause a lean condition on only one side or cylinder ?. Code 53 sounds like a separte problem that may just be more noticable when things are lean. Am I on the right track? Thanks again for the help.

 

[MrShorty]

Double check those codes, on a '94 you should be getting three digit codes, not a mixture of two and three digit codes.
I once had an O2 sensor that would only fail after a while of hard running (towing or the like). O2 sensor had developed a failure where it would fail only after getting hot.
Faulty TPS signal can cause a multitude of issues, including a hunting or erratic idle.
An out of range MAF causes issues, because the MAF is the primary input in determining injector pulse width.
And, not to ignore that the lean condition can be a fuel delivery fault. Best way to test fuel delivery is with a fuel pressure gauge.

 

[goliath]

all those codes, and a simple cause...

i had the ash on plug 4 problem too. it is VERY common. the lower intake manifold bolts have worked loose, letting oil into cylinder 4, causing the ash, and oil buildup on the o2 sensor for that side causing it to mess with the mix and throw codes. this will also cause pinging,surging, and a rough running motor.

tighten the bolts on the intake (search here for a how to), then replace the o2 sensor on that side, then clean the MAF(search here for a how to also), reset the computer, then it should run like a dream.