87jw

I have a 1987 jeep wagoneer limited with the 4.0l .
it runs smooth at idle and good at wide open throtle, but around 2000 rpms it spits, sputters, and backfires thru the exuast. I have done a compresin test, tune up, new tps, cam and crank sensors are new, new injectors, and cannot find a vacuum leak or intake leak.
anyone got a suggestion on what the problem is.

Nick-B

I'm gonna guess lack of fuel, so either a plugged fuel filter or weak fuel pump.
Have you been through Cruiser's tips?
http://cruiser54.com

cruiser54

Tips 1 through 5.

How was the TPS adjusted?

87jw

Nick-b the fuel filter is new and checked the fuel pressure at the rail and that was fine also. Sorry forgot about them in the original post. I am new to this forum and did not know about cruisers tips, but I have been reading up on them today. Thanks for the info. This is my first jeep so I am learning as I go.

87jw

I don't remember exactly how it was adjusted but I put the new one in the same adjustment as the old one. Also tested the old one and got the correct readings so probably didn't need to put it on anyway.

ajpulley

At around 2,000 RPMs, at what load are you referring to? Tooling down the road casually, or heavy on the go pedal while running through 2,000?

87jw

sitting still or moving. at idle it's smooth and I can go straight to the floor with the pedal and it revs great but if I try to gradually increase the rpms or accelerating starting from still , once it gets to around 2000/2200 rpms it starts missing, sputtering, and backfires thru the exuast and then cuts of if I try to keep going. I can let off and go back to idle then push to the floor and it comes alive. It's just in mid throttle or gradual acceleration.

67 GMC

X2 on both. I would bet weak fuel pump on it's way out. Have you got at least half a tank of good fuel in there too?

cruiser54

The TPS must be adjusted.

http://cruiser54.com/?p=54

But hell, Tips 1 through 5 need to be done also.

ajpulley

I'm leaning against fuel flow/pressure issues. At WOT, the pressure is at it's highest, and you're not experiencing the issue at that point. If it were a fuel pressure issue, whether it be the pump, or the thermal vacuum switch that allows the regulator to reduce fuel return thus increasing pressure, I would agree. And, if you have no issues at WOT with full load, I also don't suspect the filter or pump.

Re-adjust the TPS carefully, and re-check the voltage after you tighten the last screw. Check the small hard plastic line that leaves the MAP and enters the rear left side of the throttle body.

Additionally, the only direct item that remains the same at idle and WOT is the EGR valve, which you're not experiencing the issue at these two throttle position events. And, you're not experiencing the issue with no load while you run unto and surpass the RPMs you indicated. In my mind I'm trying to rule out an EGR issue. Have you removed it, cleaned the seat, and installed with a new gasket?

cruiser54

And, this problem can be caused by poor sensor grounds.

DFlintstone

Please clarify for me. The exhaust, not the intake? Are you pretty sure there?

cruiser54

Back away from the keyboard and get busy on tips 1 through 5.

freegdr

Morning Major.

cruiser54

Morning General.