'94 2.3L ranger, high idle issue.

[jinx44]

I just bought a '94 Ford Ranger, 2.3L, 5 speed, 2wd with 199,000 miles. It has a slight miss/hesitation at cruising speeds and lower throttle position.

KOER scan shows code 411---Cannot control rpm during KOER low RPM check.

The idle speed was 1180rpm, TPS at .98v, IAC duty cycle 0.0, MAF around 1.1v.

The TPS is not slotted for adjustment.

If I turn the idle screw down, I can get the IAC to command 10-15% duty cycle and it will idle at 720rpm. However, my TPS voltage is down to .83 and it still has the miss.

I checked for vacuum leaks and could not find any. Since intake gaskets are cheap, I put a new set on, checked the intakes for any cracks, and went over the vacuum hoses as I went back together with it. The only vac hoses are for FPR, EGR, and A/C controls. Capping them one at time did not change anything. Since putting the gaskets in, I have sprayed 3/4 of a can of ether around everything and still no sign of leaks. I also replaced the PCV valve to fix vacuum on the crankcase, and replaced the ECT with the updated Ford kit since I had the water drained to remove the intake. While I was there, I replaced the spark plugs and wires with the recommend Motorcraft parts. The old plugs had 15k miles on them, and all looked fine. No sign of coolant, oil, or rich/lean on any cylinder.

I have access to a wrecked truck for parts, so yesterday I tried swapping the TB. With the TB and TPS from the other truck, TPS is at .94v, idle still at 1180, and IAC still commanded 0.0.

This morning I swapped the IAC from the wrecked truck in case it wasn't closing properly. Neither IAC closes completely, so I am guessing that is how they are from the factory. But even with the new IAC, everything is the same.

I am thinking about slotting the TPS so I can turn the throttle blade down and still keep .98-.99v. However, there is obviously an issue somewhere and I would rather fix that issue than bandaid it.

When I was on the way home with this truck a couple weeks ago, I had to make a stop at the store. When I went back out to leave, it wouldn't start. It took a few tries, then it fired up like nothing was wrong. When I got home, I ran the KOEO codes and it showed a PIP/CPS erratic signal code. I have put 500 miles on it since without a no start issue or with that code coming back.

I am considering replacing the CPS while I have the timing cover and all off. I just hate to keep throwing parts at it though.

Any ideas?

 

[jinx44]

I also checked cam timing today. The previous owner said he replaced the timing belt about 15k miles ago as preventitive maintance. The crank and cam are lined up correctly, but the aux pulley has a mark on it and I can't find a corresponding mark on the timing cover.

 

[arco777]

Most posters in this particular forum section are going to be familiar with 91-94 Explorers. All of those came with the 4.0. The 4.0 is a whole other animal and is an OHV design as opposed to your SOHC. If you don't get an answer you like in this thread you might try posting in the Ranger section of these forums. Or at The Ranger Station.

The TPS on the Explorer motor is not slotted for adjustments either, but most people (myself included) drill out the inserts to allow it to be adjusted. The stock TPS, assuming proper wiring, is not always set correctly from the factory and being at .80v-1.00v is not uncommon. I would try setting the idle screw manually to whatever is spec'd as factory adjustment for it, and adjust your TPS to the proper voltage.

I wouldn't suggest throwing any parts at it - that almost never works. If you suspect a sensor, check it with a multimeter first. For instance, the two links below have some good info on checking your CMP sensor.

http://en.allexperts.com/q/Ford-780/2010/4/95-2-3-start.htm
http://www.autozone.com/autozone/repairguides/Ford-Ranger-Explorer-Mountaineer-1991-1999/ELECTRONIC-ENGINE-CONTROLS/Camshaft-Position-CMP-Sensor/_/P-0996b43f802c5420

 

[RangerX]

Moved to the Ranger forum. :rangertan: