4.0 running like a motorcycle out of gas...

[JoshT]

Hey folks,

I know I haven't been around much in a while, but I need help.

For a while now my 99 Ranger (4.0, 4x4, Auto, 120+K miles) has been having an idle problem where it would idle rough as hell when first started up. It was most noticeable after you first started it and shifted into reverse, after maybe 10-15 seconds it'd smooth out and idle properly.

Yesterday when I was coming home from work I noticed that the engine was running a little funny. When I was cruising along at highway speeds, with no abrupt changes in speed, it felt like a motorcycle that's about to run out of gas (at least that's the best way I can describe it). Going on the thought that it may not be getting enough fuel I assumed it may be the fuel pump or regulator, so I did a pressure test. Well the dang thing holds steady at 60-62 psi in both KOEO and engine idling tests.

I had thought about bad gas but I drove the truck back and forth to work for 2 days with no problems on the same tank of gas, and it's the same station I used for my previous couple of fill ups with no problems. No CEL either FWIW, may not have driven it enough to get one since the problem started though.

Any suggestions as to where my problems may lie or other tests to perform?

 

[Big Jim M]

Josh although you may THINK of gasoline first off... Chances are it is lectric. It could be any number of lectric problems. From old worn wires or plugs to sensors.. Bad idle can be ox sensors or iac or map or any number of things.
Big JIm

 

[JoshT]

Josh although you may THINK of gasoline first off... Chances are it is lectric. It could be any number of lectric problems. From old worn wires or plugs to sensors.. Bad idle can be ox sensors or iac or map or any number of things.
Big JIm

I KNOW that there can be other causes, but due to my experiences with other types of vehicles and how easy it is to check the fuel was just my the first assumption. I thought of gas first because as I said how it acted was exactly like my motorcycle does as it's running out of gas. I checked gas first because because there was no CEL or DTCs and it's easy enough to hook up a fuel pressure tester.

Wires and plugs have been recently replaced (since it hit 110K miles). I cleaned MAF sensor a month or so ago when I changed my oil. Figured since it had been a while it may have needed it, cleaned it in the proper method and did not touch the elements. The O2 sensors were replaced somewhere between 90K and 100K miles due to a mechanic's suggestion that it may have caused a couple of DTC's, there was nothing wrong with them though it was the Bama X-Cal 2 tunes, Doug of Bama chips tweaked the tunes and fixed the problem.

As for the IAC I though it would only happen at idle, and would happen all of the time at idle not only at initial start up.

 

[JoshT]

Come on folks I know there have to be some suggestions to check out before I go getting a diagnostic scan run on this thing.

 

[MAKG]

No, a diagnostic scan is the place to start. Guessing will only delay it.

 

[almostclueless]

MAKG is right; unless you have the knowledge and tools to properly monitor various voltages and signals correctly (and MAYBE a compression check), a diagnostic is the best way NOT to throw parts at a vehicle.


Welcome to the fun world of computer controlled engines. Even the throttle is electronic on some vehicles.

 

[Ranger44]

My instincts would tell me that's not a fuel pump but more a sensor. But maybe have it checked with a scan tool like mentioned before.

 

[JoshT]

Well since the soonest I'll be able to get it scanned will be tomorrow afternoon (and that's if I don't have to make an appointment) so I was wanting to do what test's and checks I could before that time.

As I said I have a X-cal 2 which will read codes and can also data log, but it's not throwing codes and I wouldn't know how to decipher the data log.

 

[Ranger44]

Do you have a Digital Multi-meter and a chilton? They shoud have test procedures for the varous sensors. Check the TB being gummed up, etc. Go for a thorough visual inspection.

 

[rags]

Have you happened to notice any lose of coolent?

 

[JoshT]

Yes I have. I've got a leaking freeze plug. It's been leaking since I got the truck. It hasn't gotten any worse since then and with this truck truck being my main mode of transportation I was just topping it off as it got low. I was already planning to fix that plug this year and since I've got my '84 running again I'll probably do it the same time as I fix what ever the current problem is.

 

[JoshT]

Was told today that what I was feeling is a "dead skip" and the mechanic said the first thing he would do is check the plug wires. Said since it was throwing no codes that it was most likely firing the plug but shorted to ground, probably inside the plug boot. He is my best friend's granddad and about as honest and trustworthy of a guy as you can find. He's also a professional automotive mechanic, actually had car dealers competing over him when he left his last job. So tomorrow I'll pull the plug wires and look for the signs he mentioned and also check for carbon tracing on the plug insulators. If I see signs on either I'll replace what I find, and if I don't find anything I'll probably replace wires anyway to be on the safe side.

 

[JoshT]

Found traces of arcing on the inside of the #1 and #2 plug boots, also had alot on the number 2 plug insulator. Replaced the plug wires and those plugs with no improvement. Tomorrow I'll go get more plugs and replace the rest of them, though I doubt it'll make a difference.

If this means anything, and it probably will. Though the skip (for lack of a better word) is there all the time, when it's under a load starts shaking real bad. Namely when I'm going up hill under light throttle. Normally without adding more throttle it'd just loose speed but this thing is, well I guess it's bogging, but as I said it starts shaking like crazy.

If I don't get somewhere by next Tuesday it'll be dropped off with the guy that ran the diagnostic test on dad's truck.

 

[JoshT]

Went back and replaced all of the plugs. When I pulled the #3 plug it to had signs of arcing. I guess I just got a bad set of plug wires, because it's running fine now. Odd that it was the three short wires that had a problem, only on the right bank. Now I just got to get around to replacing the leaking freeze plug and need to replace the driver side valve cover gasket. If I have to pull the engine to replace more than one (or even just the one) I'm thinking about installing a set of headers while I have the engine out. So who makes the better headers for this truck. I'm not studying having chrome or ceramic coating (high cost for a non-show daily driver with a stock looking engine bay), but I also don't want them to be all rusted in a year or two.

 

[289-tiger-]

Headers are a great idea for the non daily drivers and cars without emissions, not for a vehicle you intend to use. Stock would be the best way to go. A 4.0 Ranger is not a 12 second machine and the money would best go toward the rising fuel cost when you pump no matter how cool it looks.

Just a suggestion