Starts fine, drives fine, bucks, sputters and dies randomly?

[tayman]

is that the white plug lookin thing on the inside of the driver side fender by the air box

The CPS is bolted to the top of the transmission bellhousing. the plug is above the intake manifold, very near cylinder 6

 

[tayman]

Alright Guys, I want to go to sierrafest next month, and I want to not worry about my engine on the way.

I Actually swapped in the NEW TPS the other day, and that hasn't solved the issue either. It's adjusted properly, I checked before and after torquing the bolts down.

What were our other thoughts? Computer ground, potentially CPS, then what?

Symptom update: It hasn't died in a long time, but it "bumps"... it drops sharply in RPM's but comes back from it. Sometimes it'll do it a few times in a row, then not again for a while. Sometimes at speed, but mostly at idle.

 

[cruiser54]

Unplug the TPS. Probe the center wire in the harness with your meter set to 200 or so ohms. Touch the other lead to ground. What's the reading? Should be below 1 ohm.

 

[Ecomike]

One of my favorite things to do on these old Jeeps is to grab a can of good electronics cleaner and unplug every engine management connector in the engine bay one at a time and spray/flush each one and plug it back in.

Based our recent discussions and your piggyback ground findings it just dawned on me that when I ran new grounds for my 87 TPS, I never checked the fuel injector grounds!!!! I did check the O2 sensor grounds, and maybe the IAT sensor ground and MAP ground, but never really checked the FI grounds.

I still have a slight miss at low rpms that I never solved.

 

[cruiser54]

Based our recent discussions and your piggyback ground findings it just dawned on me that when I ran new grounds for my 87 TPS, I never checked the fuel injector grounds!!!! I did check the O2 sensor grounds, and maybe the IAT sensor ground and MAP ground, but never really checked the FI grounds.

I still have a slight miss at low rpms that I never solved.

Well then, get to work. LOL

I'm gonna start ohming out the injector and the other sensor grounds as a matter of course from now on.

 

[tayman]

Unplug the TPS. Probe the center wire in the harness with your meter set to 200 or so ohms. Touch the other lead to ground. What's the reading? Should be below 1 ohm.

dude even the ground strap lead reads more than 1ohm. Maybe it's just my multimeter...???

 

[tayman]

dude even the ground strap lead reads more than 1ohm. Maybe it's just my multimeter...???

oops, definitely the multimeter. I used a different one (analog), and the ground is so good you might as well touch the probes together.

 

[cruiser54]

Now do the same to all your injector grounds, MAP ground, CTS ground, and IAT ground. CTS, MAP, and IAT grounds will be brown with white tracer. Injector ground is black.

 

[tayman]

Grounds all seem to be good. The ECU case is well grounded also.

I think I need a better multimeter, though. It's hard to read either of mine.

 

[tayman]

the reason I say that my multimeter is hard to read, is that the digital meter, when set at 200, already reads 1ohm with the probes touched together. It SHOULD read 0. So something seems to already be wrong there. ALL of my grounds read about 7ohms on the 200ohm setting. except the IAT and TPS which read at ~15. That said, I put the analog meter on all of them as well, and the needle SLAMMED past 0.

 

[mickey_00xj]

When you touch the two probes together the meter should read around .3, if it reads 1 that's not actually that bad. Sounds like some impedence in your leads causing more resistance than normal. That being said and rereading your post your meters are perfect. Put the ohm setting on 20 and it'll read .1 when the probes are touched and .7 when you're checking your grounds, which is really good considering.

Sent from my A854 using Tapatalk

 

[tayman]

Well, I don't have a 20 setting, so 200 is as close as I get. I believe the analog meter is set at 2000ohm.

so being on the higher setting, the ~7ohm ground reading on all the injectors and the MAP is actually good then, correct?

Does this then mean that I should replace the grounds to the TPS and IAT sensors?

 

[Ecomike]

Sounds to me like you have a ground problem, and possibly a meter operator and or meter set up problem.

Always check the ohms for zero by checking, contacting, the test leads together. If the meter lead to lead reads .5 or 1 or .15 then that is zero, unless you have an old style adjustable analog with a zeroing knob, in which case you can zero the test system first.

The difference "C" (A-B=C) between that reading, and a measurement on the jeep ground is the ground system resistance, which needs to be less than 1 ohm!

3.4, 7 ohms and higher, like 15 ohms is your problem!!! Congratulations!!

 

[tayman]

so how do I fix the grounds, then? run new ground wires to the block or chassis?

 

[cruiser54]

PM me your email and I'll forward you what I did to fix the problem. It's easy.

I can't post it up here or I would. Maybe you can.