CPS, TPS, and Stutter or bucking

[occasionalwrench]

So, I'm new at this. Been lurking here for a long time and have tried searching threads. What I've got is a 1988 XJ, 4.0, 223000 miles, automatic transmission. Refreshed sounds, cleaned C101, replaced fuel tank, fuel pump, fuel filter, and injectors. Still needs plugs, distributor cap, and plug wires. Been working on this thing for awhile. It starts good, idles nice. Before it's warmed up it has a stutter. I'm not sure wether it's the transmission or engine. I don't have a tach so that makes it hard to tell. Not exactly sure what the best way to tell would be. The stutter happens between 30 and 50 mph at part throttle. Seems from the treads I've been reading the tsp and cps are possible culprits. I've checked the sensor grounds after refresh and have about 1/2 ohm and it's steady when I wiggle around on the harness. I have adjusted the TPS according to Cruisers write up. Still stutters. Checked voltage on the old CPS and it was .25 or so volts. from what I read it should be .5 to .8 so changed to a new NTK cps. Checked voltage again and there is no change. Still right around .25 volts. I'm checking with a low end Fluke digital meter so it should be accurate. Not sure where to go with that. Still starts good and idles nice. Any ideas on where to go from here. Thanks for reading.

 

[phydeaux33]

I have had I believe the same problem you have (88 4.0 Manual)? Everything runs great but has a slight stutter at RPM, I have been able to track it down to when it goes into Open loop at WOT (Got a REM II from Nickintime for my birthday wish I had it 2 years ago). According to the reader when it hits WOT and switches to open loop it will give me a few hiccups and then be fine so now I got to figure what is happening, I believe it to be fuel related but have yet to track it down. I will keep an eye on this post an inform any resolution if I come to one.

 

[occasionalwrench]

Thanks. Thats another thing to consider. I dont have a REM, yet. I keep watching to see if and when they are in stock so I can get one ordered. Mine is an automatic transmission. It almost seems like it could be trying to shift between gears but I’m not sure. Thats why i was thinking TPS but it’s now adjusted correctly and I think it seems to sweep smoothly as best as i can tell with a digital meter. I have tried adjusting the kickdown cable also but it was in adjustment. I’ll keep looking for an answer too. Thanks again.

 

[phydeaux33]

Thanks. Thats another thing to consider. I dont have a REM, yet. I keep watching to see if and when they are in stock so I can get one ordered. Mine is an automatic transmission. It almost seems like it could be trying to shift between gears but I’m not sure. Thats why i was thinking TPS but it’s now adjusted correctly and I think it seems to sweep smoothly as best as i can tell with a digital meter. I have tried adjusting the kickdown cable also but it was in adjustment. I’ll keep looking for an answer too. Thanks again.

You may want to reach out to Nick I just got mine over the summer he had got chips back in (his web site does not reflect that), I spoke with him the other day and he will be back in the office in December. It was probably the best 220 dollars I spent on my rig (probably would have saved me that much if I got it when I bought the Jeep and started chasing gremlins).

 

[mewz99]

Distributor indexing made a big difference for me with missing/stuttering.

Distributor Indexing

Remove the distributor cap and cut a “window” into the side of the distributor cap at the #1 spark plug wire post . The “window” should be large enough to allow easy visual …

cruiser54.com

 

[occasionalwrench]

Well a new distributor cap, rotor, plugs and wires are on order. Probably would be a fine time to go thru the distributor indexing. I have read about it but since this problem is a recent developement I haven’t done it yet. Maybe I should. Thanks for the suggestion.

 

[occasionalwrench]

I may not be done because i havent indexed the distributor yet and i should but my problems seem to be solved. The solution. Basic tune up parts like i have read in threads before. The plugs appear to have been changed a loooong time ago. The gap was probably doubled. So plugs, plug wires, and distributor cap and rotor and no more stumble and buck. So in the process i learned to adjust a TPS, change the CPS, and to look for the simple solution first. Thanks for helping.