Acceleration sputter/missing

[LarryH88bt]

88 4.0 auto.  Recently did a lot of cleaning like the TPS, IAC, tightened manifold, and new grounds.  Now it won't accelerate smoothly almost like the ignition is missing or there's a cylinder missing.  It idles fine, it just wavers a bit, and it will rev up when stationary.  Once in drive it will accelerate fine to about 2000 rpm and then starts to miss.  It accelerates eventually but it doesn't rev like it should.  I played around with the distributor, got a little better but did not solve anything.  Mash the gas pedal and it will lul and then surge and miss.  Plugs, wires, cap, rotor are relatively new.

Fuel seems to work just fine, I can even smell a little too much fuel at the exhaust. 

[joester1908]

Did you adjust the TPS after reinstalling it? (assuming you took it out because you cleaned it..?)

[88ComancheMitch]

Crank position sensor? I had a problem when I got to 45 MPH, that what it ended up being. Sounds about the same. 

[joester1908]

I'd start with checking what you messed with

[thejim42]

I'd start with the tps. That's what my issue was

[relyt120]

Make sure the vacuum line at the back of the Valve cover isnt collapsing or kinking. had a similar issue like this but not exactly the same, easy to check though so worth a shot.

[LarryH88bt]

I did adjust the TPS to spec.  I'll check vacuums again and the CPS, that's about the only think I haven't looked at.

[LarryH88bt]

Tested TPS again, fully open it should read little less than 4.8 and I get 4.3 and then closed it should be above 200 milivolts, I have 800.  That's according to my book.  Then I remember reading somewhere closed it should be 8.4, mine was set to 8.6, i think I played around to see what idled better and 8.6 was better, so not quite to spec but the TPS is within in working range.

 

The CPS, checked the resistance and it was giving me numbers all across the meter options, the book said it should read nothing at all or just a 1 indicating its fully open, yes? 

[LarryH88bt]

I replaced the CPS with a Standard Products CPS, same problem.  Going to try the distributor indexing.  TPS is now at a genuine .84.

[LarryH88bt]

Reset the timing a few times now, advanced and retarded it multiple times with plenty of back firing.  It seems to like the rotor well in front of the #1 terminal in which case it revs and idles pretty good.  But, once on the road past 2500 rpms it still sputters and hesitates.  The thing, there is no notch on the crank wheel.  All I have are two 1/2 inch holes; its guess work to find true 0. 

 

Is it really that sensitive to where a single degree can mean a big difference?

[Knucklehead97]

Possibly the MAP sensor? My MAP line melted shut one time and I couldn't get past 2500 either. Just I had literally NO torque. Maybe the lines not completely shut, but enough to cause a problem.

[cruiser54]

Click on the link in my signature and go to Tips 1 through 5 and maybe 27.

 

For TPS adjustment go to Tip 8.

[deziped1]

Vac line from MAP to back of throttle body (TB) leaking maybe. Is it connected to TB or maybe sucking air at MAP end.

[LarryH88bt]

Gave up for a few days and then went back in and found the damn notch on the crank wheel.  Was pretty hard to spot.  Once I found it I was able to set the timing right.  Runs good enough now, just a weird idle that it's always had.  9 times out of 10 its the simpilest thing that gets me.