1997 Ford Explorer XLT 4.0 SOHC 79,000 miles with CEL. Initial codes PO 171 & 174 in Oct/2004. Initially cleaned the IAF only and that cleared the CEL for about 4 weeks and then CEL came on again. Checked the MAF and seems clean after spraying it with appropriate cleaner. Attempted to get the PCV valve assembly apart but have not done so because I'm afraid I'll break it. Finally after the CEL was on for approx 1 year I replaced the IAF with a Borg Warner part. The original IAF was pretty rusted. I had read where Borg Warner makes a lot of OEM parts for Ford. The CEL still remained on (but now reading Code 171 only). But now the vehicle has a miss/stumbling immediately on initial start up. Then it idles okay. Previously this miss/stumbling was not there immediately but would begin after 6 or 7 seconds. Also once in a while the vehicle will cut off when idling at a stop point. It had done that same thing back in Oct/2004. The intake manifold o-rings & gasket have not been replaced. This is my girlfriend's vehicle and we hate to take it to a Ford dealership and have them do their thing and then still have the CEL problem. I'm assuming they would not fix it and then we're out all that $$. I've read a lot about this problem on this forum and other forums. 17.5 mpg and a strong runner. No tune-up for 5 years or so. What about an independent tune-up shop? We would appreciate any suggestions.

 

The common cause of a P0171 and 174 and rough idle, especially with the engine cold, is bad intake O-rings.
If your dealer is like where I work they've probably replaced lots of them and have them in stock.
Since it hasn't had a tune-up in 5 years I'd probably replace the plugs and fuel filter as well.

 

Sounds good to me. I think I've read where Explorer owners replace the belt tensioner at the same time they have the o-rings done. Is this a good idea? Thanks, Racerguy.

 

That would be the timing chain tensioner. It comes in a kit with the o-rings.

 

Took in my girlfriend's 1997 Ford Explorer 4.0 liter SOHC today. Approximately 78,000 miles on it. The vehicle had the CEL with code 174(previously code 171,too) and it was an independent shop with a supposedly good reputation. When I mentioned to the service advisor that AutoZone and Schucks had read-outs indicating these PO codes then he sort of laughed and said his "up-to-date software" would get to the root of the problem when the diagnostic test was done. They do work on State Patrol cars and RV's,too. The mechanic replaced the spark plugs,fuel filter,air filter and pcv filter. He also put in a can of KG 44 for the fuel injectors. They wanted to replace the ignition wires and clean the MAF but I told them not to do it. I had already cleaned the MAF and replaced the IAC. I mentioned to the service advisor that I had read where it was common for this vehicle to have problems with the intake manifold o-rings. The final work-up report showed that they checked the o-rings and there was no charge. Wouldn't that take at least 30 to 45 minutes to check them? If it took that long I have to believe they would have charged me. Am I out of line thinking that they were not checked? I was told the fuel filter was gummed up. It was just replaced 15,000 miles ago and the engine runs fine except for initial stutter when starting it in the morning or when stopped at a stop sign/light. BTW when I checked under the hood afterwards I noticed the lamp/light on the underside of the hood was missing. I have no proof that it was in there when driven in but I know it was there a few weeks back. I can't help but be suspicious of the o-ring and underhood lamp issues. Am I overreacting here?

 

The O-rings can be checked without taking anything apart but the engine has to be cold.
With the engine cold (sitting a few hours at least), you watch the short term fuel trims on a good scan tool that reads live data, while spraying carb cleaner or something similar at the joints on the intake where the O-rings are. If the short term fuel trims change when spraying then you have a vacuum leak.
The tech may have removed the bulb to keep the battery from draining and forgot to replace it.

 

Thanks for the replies, Racerguy. My girlfriend took the vehicle back to the place and they replaced the light bulb for free. The bottom socket portion of the bulb was still in place so I'm guessing the mechanic might have raised up and busted it. Anyway they took it out and replaced it for free. So far the CEL has not come back on and the vehicle is running great. It will be interesting to see if the gas mileage improves at all.

 

Likely then that they re-torqued the intake manifold bolts. It's a quick fix but wont last forever.