'91 E.B., 4.0 Engine Pob.?

[Boman01]

I have a '91 Eddie Buer with a 4.0, and it shudders at 45-55 mph in overdrive. It almost feels like when you have a manual and shift to early and the rpms are to low and causes the engine to struggle. I have had the tranny checked and there is nothing wrong with it, so then i had the engine hooked up to a computer and there werent any codes in it and nothin showed wrong. I had one mechanic say he thought it was the MAF sensor so i got a new one, no change! The next mechanic told me he thought it might be the injectors, but wasnt sure due to the other many possibilites it could be! Also i have been told it isnt common for these engines to have faulty injectors so now i am lost! And i have tried many injector cleaners, once again with no change!Any suggestions?

 

[Bill Kemp]

I would change the spark plugs and wires. Most any problems I have had, like what you mention, were cured by plugs & wires. And if that is not it at least you probably would have needed them anyway.

 

[KEbert]

There is a little shrader valve on the side of the intake manifold towards the rear that you can blow compressed air into while the engine is running to clean the injectors.

Bill is probably right though with the plugs.

 

[Boman01]

i have changed the plugs and wires twice now and that isnt it . It has had this problem since i got it and i guess i figured it would smooth out but it hasnt.i will have to try tht with the injectors. any more opinions are much appreciated. thanks. Oh yeah also the coil pack has been changed.

 

[Bill Kemp]

Vacume leaks? Got me by the @ss....

 

[SteveVB]

If you ran the codes and none showed up, and its not the MAF, I would look at the TPS, and also the Torque Converter lock up. Sounds to me like the TC but from the description its hard to tell.

Does it shudder at the same RPM when the trans isnt in OD?

 

[zensius]

I would definitely look into the TPS. When it starts to go bad all sorts of other things get blamed. I've replace tons of good parts hunting down a problem that turned out to be a TPS. TPS. TPS. TPS!

 

[Boman01]

It does do it at around the same rpm when out of overdrive but it is almost not noticeable. If you didnt know about it you wouldnt be able to tell. It seems to only do it when the most drag is on the motor. Where is the TPS on this motor and what would be some signs, if any, that you could tell by lookin it over that it is bad? Thanks for the help.

 

[rmob]

Boman01
I've been living with the exact same problem for a month and your description is on the money...Had the tranny check & MAF cleaned with no luck...Hopefully someone out there has an idea.

 

[zensius]

The biggest giveaway that it's the TPS is that problems happen at about the same RPM or speed. What's happened is that the TPS had developed a flat or dead spot where the computer can't read you speed. The TPS is located on top of the throttle body on top of the engine. It's usually black or dark grey and has a few wires running out of it. There's a simple way to check if it's working properly with an OHM meter. I just don't know what it is. Someone here must know the procedure.

 

[Boman01]

cool i will probally try testing the TPS tommorrow, by swapping one from a different engine, and possibly if that doesnt work i will try blowin out the injectors from that valve. thanks for the suggestions, and "rmob" i will let ya know if any of this works so maybe we can both have our troubles solved.

 

[SteveVB]

DONT BLOW OUT THE FUEL RAIL

The schrader valve is for testing the fuel pressure and injecting cleaners, blowing air through it isnt going to do anything since the injectors will be closed, they wont open unless the engine is running. The fuel is yunder pressure when you open that valve so be careful- the air idea sounds useless to me. Without running the engine you wont have much effect on the injectors. Plus it sounds a bit dangerous to me.

 

[Boman01]

Yeah thats something i have been debating. The last thing i need to do is spend more money then i have to! I am gonna ask some questions to a mechanic i know and see what he thinks about it . thanks again.

 

[Boman01]

well i put on another TPS today and that was not it! I talked to that guy about the injectors and he told me that if i unplugged one while it was runnin and there was no change then it is the injectors. I did this and there was only a slight change! so next i get to replace the injectors. well i will keep you posted.

 

[ChuckyD]

did you ever fix your problem???
was your X stalling too?