93 YJ spark / vacuum problem?

93 YJ 4.0 automatic

Are there any recommended procedures for checking for a spark problem?

Vacuum leaks?

tranny shop tells me that the transmission is good and that I either have a spark or vacuum problem --- I feel like I'm getting the run around but want to explore all possibilities before calling the guy a thief.

tia paul

Reply to
paul
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What is the problem? Describe what is/what is not happening with the vehicle. I take it your transmission isn't shifting right, or has some other transmission-related problem. If there were a spark problem, you would notice the engine running rough. It would be odd for spark, or lack thereof, to only affect the transmission.

Earle

Reply to
Earle Horton

The throttle position sensor is notorious forgetting a bad connection. It controls the shift points on the tranny.

I recommend an electronic spray contact cleaner on it, well all of the computer sensor plugs for that matter like like CPS. I then like to rub some dielectric grease on the plug's seal skirt.

WD40 will even work in a pinch, it just doesn't last long.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > 93 YJ 4.0 automatic
Reply to
Mike Romain

It started awhile back with slow acceleration from a dead stop then at freeway speeds if I tried to pass the RPM's would shoot up to 3500 and there would be no drive train response.

Took it to a transmission shop they did a 'rebuild' of the tranny - I got it back still had the same problem but now it was more noticeable that it was not shifting properly from 1st to 2nd - rpm's increased - no shift unless I let off on the throttle. Took it back again, and was told they tried adjusting the shift points both earlier and later with no favorable results and that they feel that there is a spark/ vacuum issue.

Now the symptoms are the same except at freeway speed it will no longer kick up the rpm's - just plods along at 60 mph.

If I shift to neutral I can get an rpm response on the freeway but not while in gear.

?????

Reply to
paul

I'll give that a try this weekend,,, thanks

Reply to
paul

Is the kickdown cable properly adjusted?

It's on the side of the trottle body and runs down to the transmission. The adjustment is a pushbutton thingy on the holddown. You move the cable end further away (more tension) to tighten up the shift points.

You can test spark with a gap tester. How old is your ignition system? Plugs could be bad, the wires could be arcing or worn out, bad cap or rotor will make for weak spark, and the coil is well known for going bad. Best replacement for the coil is a NAPA part ECHIC409 (same as the OEM part) but this has a short resistor lead and a better matched coil.

Reply to
DougW

Doug, I did adjust as per your earlier recommendation without any success.

Ignition (plugs, wires and cap) was done 2.5 years ago. What is a gap tester and how does it function?

Can I test the coil with a meter?

thanks much, paul

I should add to my descripti>> It started awhile back with slow acceleration from a dead stop then at

Reply to
paul

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Several types, I have these (this one is better for open engine bays)
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one works easier.http://www.thetoolwarehouse.net/shop/TA-23900.html It puts a known air gap between the coil and ground. The distance the spark will jump indicates how high the voltage, and the brightness indicates power.

sorta. I've tested quite a few that look good with a simple resistance check but don't actually work. So much so that throwing a known good test-coil in there is easier than piddling with the meter.

Reply to
DougW

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