97 4.0 SOHC..Rough Idle..Replace Engine ???

[dodgeman9]

I have a 97 Explorer with the 4.0 SOHC engine. It has about 121000 on it and has been maintained very well.

It has had a problem with the RPMs dropping and bouncing at stoplights for awhile. It hasn't ever cut off but it'll make you think it was. It doesn't do it all the time and I haven't been able to pinpoint when it would do it (cold, hot, AC on, AC off etc.). It just kinda comes and goes at seemingly random times. I've had it hesitate on take off a few times. It was enough of a hesitation that it made you wonder was it going to go at all then it would kind of take off and run normally. I've also thought that I could feel something that felt like a slight miss in the engine while crusing along on the interstate but it was so slight that it could have been the road. Hard to tell.

We've replaced the throttle position sensor, the IAC (twice with known good units), had the computer updated, plugs and wires, etc. and still no good.

Now for the ??? part. I took it to the local Ford dealer to let them take a swing at it. They pulled the valve covers and then called me and want to replace the engine due to the timing chain problems that have been well documented on this forum. They say that the timing may be varying enough due to the chain tension, or lack thereof, that it could cause my problem. Anybody got any ideas?

I really don't want to have to trade this vehicle. It looks almost as good as new and as I've said it has been well maintained since it was new (I'm the original owner) but I aslo don't want to drop some major bills on it if I don't need to.

I'm kinda POed that I've taken such good care of it and now I'm looking at taking a major bath on it. #$%&* poor design!

 

[ghosttrain2]

Have the upper and lower intake gaskets been replaced? The black oring seals have been replaced by red colored ones. Then there is cleaning the IAC and throttle plate, also described on this forum.

 

[2000StreetRod]

Rattle?

Did you look at the guides to see if they were broken?

If there is enough slop in the chains to cause an erratic idle then they should be making quite a racket. My rear guide was completely broken in half and the engine idled OK.

Have you ever replaced the upper and lower intake gaskets?

Are all of your vacuum lines in good condition and connected properly?

Did you try cleaning the MAF sensor? Have you tested the voltage output?

Have you replaced the fuel filter every 30,000 miles? Have you checked the fuel pressure?

Do you have any diagnostic trouble codes?

Even if you're not mechanically inclined, have the mechanic show you what's broken before authorizing $3500 or more to replace either all of the timing chains or the engine.

 

[dodgeman9]

I haven't had the intake gaskets replaced.

All the vacuum lines seem to be o.k. We've checked them repeatedly.

The MAF sensor was replaced a while back. No change. No idea what the voltage output is.

The fuel filter has been replaced. Not sure when it was replaced last, but I think it was about 10K ago.

No codes.

I've been thinking about the chain problems. It sounds like it's one of those things that needs to be fixed or you'll regret it sometime. I know the wife is scared to drive it without fixing it. So it looks like we might be trading it. Hate to. I've taken very good care of it and it looks like it. Had anticipated getting something out of it when the time came. I'll probably lose on the trade. It don't book for what I would ask for it. Ford owes me one!!!

 

[ThePhoenix]

I haven't had the intake gaskets replaced.

there's your sign....

 

[chadfire]

i would put the money into and replace the bad parts and keep the truck i had to replace all of my chains and its running fine if you need help let me know and i will be willing to help you get yours running and back on the road

 

[burningsno]

exactly the same issues with mine it mostly does it when its warm. its annoying but it doesn't seem like it would just stop working altogether. I've checked most all things except the timing chains which don't seem to make a lot of noise, and the intake gaskets which may be the problem. Mine has around 330k so if it blows up...it blows up, oh well.