Hesitation at acceleration, coughing/backfire. white plugs

[relyt120]

So I have been having an issue with my DD.

89 4.0l aw4 2wd MJ

 

The issue is at a certain point in the throttle I get this coughing, spitting,  sometimes backfire type of sound and a hesitation in acceleration.

If I give it gas past that point of throttle it does fine, and below the point and at idle it is fine as well.

Starts up fine.

 

I decided to do some maintenance to rule out a few things and changes the distributor cap, rotor button, plugs, and air filter.

When I pulled the plugs the old ones had a lot of residue on them.

Changed the cat a while back and the issue was still present (thought it might be clogged)

02 sensor is relatively new.

fuel pressure regulator is newer

map sensor replaced previously

 

 

 

 

 

 

I also grabbed a new fuel filter but I replaced the previous one not too long ago and will save this one for when I get a set of volvo injectors for the truck. A repair manual I was reading said that a hesitation in throttle could be a clogged injector?

 

Also when I first got the truck it had an issue with overheating so I had put a really low temp thermometer in it and the temp seldom rises above 160 F.(head gasket, radiator, and open cooling swap took care of the issue but i never changed the thermo back)

 

I had a similar issue to this before this one started but it was much more pronounced and even had the truck where it would not get to speed and would cough and spit and backfire...I finally realized my CCV line was collapsing and I replaced it and then this started.

At that point I was glad I didn't have to worry about getting virtually stranded with the truck not wanting to run right but now this issue is getting to be a nuisance. 

I decided to mess with the line some more and found that if I use a different diameter line I can change the position in the throttle that the issue occurs at.

BY THE WAY I have a newer steel valve cover and I also got the larger fitting for the intake/exhaust manifold for the rear ccv line.

 

I am not sure where I should put my time and money in to fix this issue.

 

Your suggestions are appreciated.

[big66440]

I would check your TPS sensor, first make sure it's adjusted correctly ( there's tons of info on how to do it if you search ), then I would check it with a voltmeter from the closed position all the way to the full throttle position to see if you have a "burnt" or open spot on the TPS sensor itself, also make sure the throttle body is clean.

[ftpiercecracker1]

I would check your TPS sensor, first make sure it's adjusted correctly ( there's tons of info on how to do it if you search ), then I would check it with a voltmeter from the closed position all the way to the full throttle position to see if you have a "burnt" or open spot on the TPS sensor itself, also make sure the throttle body is clean.

 

 

:agree: 110%

[cruiser54]

Click on the link in my signature and do Tips 1,3,4, and 5. 

 

TPS adjustment is Tip 8. Throttle body cleaning is Tip 11. 

[fiatslug87]

Check your EGR

 

http://comancheclub.com/topic/38225-egr-solenoid-renix/?fromsearch=1

[relyt120]

Thanks guys, I'm going to look into a few of your suggestions on monday

:thumbsup:

[relyt120]

I cleaned the throttle body and I did the tips cruiser suggested and adjusted the TPS. I believe the TPS was the issue.

my expected output was .83 and my actual output was .56.

I adjusted it and got a super high idle so I adjusted it down and incrementally took it back up until the high idle stopped.

 

It seems to have fixed my issue but it was not happening much earlier today so I will report back later in the week as i get to drive it some more.

 

Thanks again guys.