YotaTech Forums - 1994 V6 4Runner issues after timing belt replacement

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1994 V6 4Runner issues after timing belt replacement

Timing belt being replaced on my 1994 V6 4Runner w/ 5spd trans. According to mechanic (small shop) truck will not go over 40 mph and acts as if it’s hitting a rev limiter around 3,000rpms. He’s opened it back up and double-checked timing, set it forward and back one tooth - same result.

Had to replace plastic “box” below air intake as it was brittle and broke apart.

Little bit bit of background, belt failed while driving. Original owner, so well known history on vehicle. Had truck towed to one shop where I knew the owner. They looked at it, but did not want to get involved with job in case any motor work was required as they no longer do the heavier work. Current shop does not have a scanner old enough to work on this truck, but is going to contact someone who does.

Has anyone here had experience with this problem? Any advice would be most appreciated, thanks in advance.

Welcome to YotaTech.

Quote:

Originally Posted by Stillplayswithtrucks (Post 52398905)

... Current shop does not have a scanner old enough to work on this truck, but is going to contact someone who does. ...

This shop may not familiar enough with your truck to work on it. The "scanner" you need is a paper-clip. (Called the "SST" here: http://web.archive.org/web/201211190...85diagnosi.pdf )

So spring for an "old enough scanner" (paper clip) and read the codes yourself. Report back.

While you're at it, pick up a $30 timing light and check the base ignition timing. DON'T move the timing belt back-and-forth a tooth. Set it correctly and you are done there.

Thanks for the welcome and reply scope103. My mechanical (and computer) abilities are limited, so engine diagnosis is a bit above my skill set - trying to learn as much as possible though. While I initially didn’t fully understand the info in the link, after digging out my shop manuals - it makes more sense. Will post up once I have the results.

Quote:

Originally Posted by Stillplayswithtrucks (Post 52398910)

And forgive me for this question, but I did not see a reference to the SST in the provided link? Where exactly does one use the paper clip?

use the paper clip to jump TE1 to E1, count the flashes of the check engine light
https://cimg5.ibsrv.net/gimg/www.yot...cc4a7eba13.jpg

Quote:

Originally Posted by scope103 (Post 52398909)

Welcome to YotaTech.

This shop may not familiar enough with your truck to work on it. The "scanner" you need is a paper-clip. (Called the "SST" here: http://web.archive.org/web/201211190...85diagnosi.pdf )

So spring for an "old enough scanner" (paper clip) and read the codes yourself. Report back.

While you're at it, pick up a $30 timing light and check the base ignition timing. DON'T move the timing belt back-and-forth a tooth. Set it correctly and you are done there.

Shops don't have ulimited time unless the customer has unlimited money. Codes are sure helpful for narrowing things down some, but that's not all there is.

A paper clip is all it takes to read the codes, but there's a lot more that a Toyota factory scanner, or a high end proprietary scanner can do for a pre-OBD II Toyota.

I have an old Snap-On MT2500 'red brick' scanner with Asian trouble-shooting cartridges and Toyota specific diagnostics that can show all sorts of real-time data that can make otherwise difficult troubleshooting easy. It is possible to look at TPS outputs, for instance, and correctly adjust the TPS with the truck running; to determine whether the ECU is running open, or closed loop, ect, ect, ect.

These proprietary scanners and programs cost techs thousands in the late 80's and early 90's, but can be got for a couple hundred bucks today if you shop around.

Such a scanner can be worth its weight in gold when troubleshooting pre-OBD-II trucks.

I have noticed that more info will come out of my '95 Runner than will come out of the '87 Runner. Although the diagnostic plugs are identical, the ECUs of the newer ones are a bit 'smarter'.

Thanks dropzone and millball, for the great info. Much appreciated.

So after the truck was scanned, turned out to be the MAF sensor was failing, in addition to a few cracks in some of the plastic components of the air intake. Air filter was due for replacement as well.

Happy to report that it runs better than it has in a long time. Shop was more than fair with me, and did not add anything more to the final bill other than the cost of the MAF (I have the receipt), air filter and some $ for the diagnosis from the 2nd shop with the scanner. I added some cash to the total and a case of beer, as he definitely didn’t change me for a lot of the time he put in. (and picked me up since I didn’t have a ride available to get there.)

Next up is a set of BFG KO2s going on this weekend. Then it will go back to him for brakes as soon as the budget allows - they only have 210K miles on them......I think it’s time:D

Thanks again for your help and input - much appreciated.