Squigglez

The Problem:

So it seems that when on the highway, around 75 km/h and up when I give the truck some throttle it will not accelerate and kind of shake. When I floor it, sometimes it accelerates very slowly and all of a sudden the normal, full power will kick in and the truck will accelerate like normal.

This happens usually from second to fifth gear around 2000 RPM, Not exclusive to highway driving.

I used to drive an 08 Jeep that had a bad coil pack and its the exact same symptoms as that.

I have changed the plugs and used the NGK V-power as recommended here on yotatech, but the problem remains.

I have an ebay cold air intake that almost sounds like it has a vacuum leak. Maybe its just sucking a lot of air. (I didn't buy it, Previous owner had it)

I'm not really sure where to start with this problem... Sensors? Airbox?

By the way the truck starts and idles fine.


1993 sr5 pickup, 302,000 kms, 5 speed.

YotaRunner001

I had the same problem. Turns out that I had a dead cylinder. Do a compression test on it and see what it comes up with

Squigglez

Did a compression test and all cylinders had a pressure of about 170 psi.

YotaRunner001

That's a good sign. I did my compression test on mine and all except the number 3 cylinder were around the 150psi range(#3 was at about 25psi). According the my Chilton's book, the cylinders should be running anywhere from 125psi to 150psi

Odin

Cylinder number 3 had a total of 25 psi or it was down 25 pounds compared to the others?
A total of 25 psi is going to one hell of a misfire.

YotaRunner001

Odin, it was reading a total of 25psi when all others were at 150psi

Squigglez

Anyone else know where I can begin trouble shooting?

bswarm

Sounds like you are describing a misfire under load. It might have a bad plug wire. Did any of the plug wires have oil on them when you pulled them off the plugs? The plug wires reach into the valve cover, sometimes oil seeps in the wells and shorts out that wire. Or is yours the coil over the plug? Same thing, might have a bad coil.

RJR

I would check the TPS. One of the functions of the TPS is to let the ECU know of rapid changes in the throttle, so the ECU can anticipate the sudden inrush of air and enrich the mixture to prevent stumbling on acceleration. Without the TPS signal, the ECU will eventually figure things out and get the mixture right, but it can take a while to get going.

Instructions for testing the TPS are here. http://personal.utulsa.edu/~nathan-b...34throttle.pdf There are also several writeups on this forum if you want to do some searching.

Squigglez

Thanks RJR ill try that.

It has been undercoated every year for the last ~20 years so that would have messed up some of the plug wires. The alternator was recently rebuilt because it stopped working due to being covered in undercoating.

Squigglez

Ive been told that it could be bad injectors. Is there any truth to this? I'd like to check them, and if I do, do I need to replace the crush washers?