• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Bucking/hesitating

It still does it i went for quick drive down dirt road and floored it and it bucked soo much and didnt want to rpms went down to under 100
 
You measure the voltage throughout the throttle range, watching for erratic movement.

An analog meter works best, the low-priced DMMs have to much of a buffer built in.

Read this: http://billyxj.tripod.com/SENSORS1/page1.html
 
Not to state the obvious or anything but I work in the automotive industry. I'm a diagnostic tech and you wont believe how many times I get back parts out of the box. Just because its new doesn't mean its good. We don't use cheap parts either but that is just the way it is. I've learned to test it before and test it after just to cover your ass. But do what peters said look for erratic movement, just do a some what slow movement and then do moderately fast and sweep it multiple times. One thing too which is less likely but some times you may want to check the signal at the pcm also. Some times the sensor is good but maybe...some where between the firewall and the pcm there is resistance and the signal drops down. But like I said, check fuel, do a GOOD visual of the wiring, check to make sure the distributor is aligned correctly and what not. Another thing you can check is intake air temp and/or coolant temp. Those, especially coolant temp, have a HUGE effect on fuel strategy for the PCM. Your coolant temp sensor can have drop outs just like your TPS. Oh one more thing, I've never been a fan of "hitting" things but you know what, it works great! Start tapping sensors with a screw driver and kind of shake and pull the wiring, not to hard but enough to get something to act up. I've narrowed down lots of problems like that. Another thing you can do is have someone put the car in gear if its an automatic and then be sure to block the wheels and hold the brakes but power brake the engine. Go to like 2,000 or 2,500 RPMs and see if you can get it to act up while you poke around under the hood. It works great, especially for miss fires.
 
WOW........I have been having the EXACT same problem......I could never figure it out, so Im just dealing with it......search for my thread maybe it will give you some help
 
I too have the same issue; I may try the distributer trick. Here is my story.
I have an 88 Cherokee with a 4.5 Stroker from Hi Tech Motors with an automatic; it has been running great for two years. Last fall it started to miss when cold, idles fine, wide open throttle is good. It will miss just off idle (mostly 1500 to 2500 RPM) till it warms up (190*), runs great when warm.

So far I have reworked the grounds in the wiring harness, cleaned the C101 connector, tried several, tested or replaced the CTS, MAT, MAP, TPS, IAC, O2 sensor, EGR Valve, CPS, Cap & Rotor, Ignition module, Plugs & wires, Fuel Pump & Filter, Fuel Regulator test good, 195 thermostat, vacuum is good.

I have not tested voltage & resistance at the ECM or tested the Cam Shaft Position Sensor.

I have a Fuel to Air gauge and I can see it go lean when it misses then back to 14.7 to 1. A friend of mine has a Snap On scanner that tells me it is going in to Closed Loop at about 140*.

My next step is to check Voltages & resistance at the ECM. Then I am going to the wrecking yard to look for an ECM. What have I left out? Anybody have any ideas?
 
I solved my issues; I found that the thrust washer on the distributor had worn out causing excessive endplay. Remove the distributor cap and see if you can turn counterclockwise the rotor as you gently lift. There should be very little movement.
Good Luck
 
I solved my issues; I found that the thrust washer on the distributor had worn out causing excessive endplay. Remove the distributor cap and see if you can turn the rotor counterclockwise as you gently lift. There should be very little movement.
Good Luck
 
Thank you I will check this tomorrow. It bucks a bit less now that I sea foamed it. But still. Mine bucks when flooring it some times. Also when cruising above 40+. And sometimes when I hit bumps in the road. My tachometer also spikes down many rpm with each "buck". It feels like maybe the transmission. But if so I don't see how it would affect the tachometer.

Going to drop my tank tomorrow and pull everything out and fix it. Perhaps it's a fuel pressure issue being that I dripped gas when I braked. Does not drip when the tank is about half full. Dripped gas through the whole inspection station today. (I made off good. Glad this new inspection rules are going in effect soon.) Fuel pump wines badly and the fuel gauge is out. So lets home this solves my bucking issue as well.

edit: Does anybody know a good way to extract r134a to put in new r134a?
 
Last edited:
You must log in or register to reply here.

Similar threads

J
2001 4.0L issues
Replies
15
Views
282
Saudade
Saudade
C
Cranking Time
Replies
6
Views
88
CBJeeper
C
F
Stumped on this one!
2
Replies
29
Views
4K
Bent
Bent
Z
1990 renix electrical issues
Replies
3
Views
95
cruiser54
C
I
High idle, smells like gas, running out of things to replace
Replies
2
Views
2K
Inverhyt
I
Back
Top