btc50

I have a 91 Toyota PU 4x4 with a 22RE. When I bought the truck, it had a bad exhaust leak between the manifold and the pipe, so listening for engine noises was rather difficult. After I got the exhaust problem fixed, I could hear a knocking noise. It happens when the engine is at relatively constant speed and from 1200 rpm up. It is very subtle if not completely non-existent when the engine is cold. It is loudest when in the 1st or 2nd gear when you are either under light acceleration or holding the throttle steady. I can't tell whether it disappears in other gears because of tire noise and straight-pipe exhaust. It doesn't do it during hard acceleration, so I thinking it isn't pre-ignition or detonation. It sounds a lot like rod knock, but the engine has less that 10k miles on it since it was rebuilt. I don't know the exact details of the rebuild, but I know it got a new head and a new timing kit. The noise is loudest in the cab (with the windows down), or when laying directly under the cab. I bought a mechanics stethoscope, but the results with it were sort of inconclusive. I can hear the noise starting a little bit beyond half-way back on the oil pan. The noise is too high in pitch to seem like a main bearing. The noise is also pretty loud when i touch the stethoscope to the bellhousing. The clutch was also fairly new when i got the truck, because it was not broke in. It is a little easier to get it to make the noise with the clutch out, but it will make it with the clutch in. Tranny in neutral or tranny in gear (with the t-case in neutral) doesn't seem to matter. As a final note, I can feel the knock coming through the clutch pedal sometimes. Any ideas?

btc50

MRecio

does the knocking increase in speed along with the RPMS?

btc50

The knock rate does change with RPM, but the pitch doesn't change. I thought of something else in regard to spark knock: While the noise pattern doesn't follow the little bit I know about spark knock, I am somewhat suspicious of the timing. The guy I bought it from told me that he did not have a timing light when he put the engine back in and the he "guessed" at the timing. I don't have a timing light either, but I don't mind spending the money and checking the timing if anyone thinks the noise could be related. The engine seems to have plenty of power given the stock 4.10's and 33 tires. (i will be down-sizing tires someday). Also, the ECU has the following codes: 12, 13, 21, 41.

I know 12 and 13 are distributer related.

MRecio

Would highly recommend getting a light and checking timing even if it is not the cause of the knock... guessing at the timing is very bad and isnt worth it when it only cost 50 bucks for a light to do it right...

btc50

Timing definitely seems to be the main cause. When I first connected the timing light with the TE1 to E1 jumper in place, I got a reading way off the scale, like 30+ degrees BTDC. Unfortunately, I was only able to bring it down to about 12 degrees BTDC before I ran out of room in the adjuster slot on the distributor. I believe 5 BTDC is the correct spec with the test connector shorted. I read somewhere that if the throttle position sensor is malfunctioning, you will not be able to get the timing correct. I know I have code 41 on the ECU, which is "TPS error." Does it sound plausible that the TPS could cause this timing issue?

Targetnut

The TPS malfunctioning will likely preclude correctly adjusting the timing.

If your timing is so far of as to create a knock under a no load condition, it would likely be running horribly if at all. Since it is impossible for me to listen to it through the internet, I would suggest you find a tech that is experienced with your truck and have him/her listen to it and let you know what you think. There are so many things that can create a "knocking" noise and some are hard to distinguish from each other even in person. If it makes the noise even in gear when stopped it is almost certainly not the transmission. Could be a clutch issue or even a loose flywheel.

MRecio

you wont be able to set the timing correctly with the TPS not working right. the test the TPS with an ohm meter it may need adjusting or it might have gone bad... check the FSM on how to do it...BTW a lot of folks advance there timing to 12-15 BTDC to gain a lil pep and say it smooths idle and gives them a lil better MPG... but it it really was at 30BTDC then that would have been the cause of the knocking or pinging as that is way to far advanced.

n4ynu1010

TPS Check Specs :
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

93 Online FSM :
http://personal.utulsa.edu/~nathan-buchanan/93fsm/

I beleive the 93 FSM should acommadate you if you need a reference for anything , the first link is for the TPS which is also in the FSM but the first link is a bit more user friendly , TPS can cause some timing adj problems so check that and go from there but I would abstain from driving if you can until you find the problem .
If the TPS is not causing your timing problem then I would suspect the Distributor is a tooth off maybe or timing chain maybe the same ?
Put the #1 cylinder on TDC and check the timing mark , should be on the mark at 0 degrees , then check your rotor on the distributor and make sure it is on #1 about midway of right to left travel .
I all that checks out then you need to zero in on the sound and start investigating , I have seen clutch installs go bad in more ways than one (throw out not properly installed or backwards even, bad or broken friction disc , pressure plate finger damage in install) like over-torqueing pressure plate or flywheel bolts and then they break when the drivetrain gets hot or likewise not torqued and back out and any of these could cause the knocking and or vibration , keep us posted on your findings .

btc50

The tps is working as best i can tell. All the tests with a multimeter passed, and I did a continuity test on all 4 wires between the TPS and the ECU. The ECU trouble code still shows up (i did the reset procedure), but there is a noticeable RPM drop and timing drop with the test connector shorted. I still could only get the timing down to about 7-10 BTDC before I ran out of room in the adjuster slot in the distributor. I suppose the distributor could be off a tooth. I'll do that check procedure later today. I also managed to get the RPM signal errors to go away. It does seem to idle a lot smoother now and I was able to back the idea speed back down to nearly spec and it still ran smooth.

I known I said that the timing adjustment seemed to affect the knocking noise, but after a second day's test, I think it just reduced the valve train and overall engine noise, but not the knock. It feels and sounds like the knock is coming from under my feet while driving. It wouldn't surprise me too much if something was loose in the clutch, considering some of the other bolts I found loose on the transmission and front diff. mounts. The guy I bought the truck from was a dumb A$$.

Is there anyway to inspect the clutch without pulling the tranny back? I havn't found an inspection cover, but I could have missed it. If not, I will be taking in next week to have the tranny pulled for a clutch inspection. There is another noise that definately sound like it is coming from the clutch: a fast rattle right when you push the clutch in to change gears while accelerating. It only lasts about half a second, but it is pretty loud.

n4ynu1010

That last one sounds like a throw out bearing / pressure plate problem , if you pull it off make sure they check that your pilot bearing in the crank end is good , I have seen people replace many clutches and not replace a bad pilot bearing or tear it up during install, if that is destroyed it could produce a knock of sorts .
Just my limited knowledge looking at my 5spd manual ( '91 3.0 ) and I see no real way , the clutch arm sometimes has a removable dust boot but vision is very limited at best .

Targetnut

if you think the noise is coming from the bell housing then your best bet would be to inspect it before you tear somthing up

If the flywheel is loose you may have already damaged the cranksaft and flywheel.

btc50

I finally got it to the shop today. The guy said it sounded like a bad pilot bearing from his initial listen. Unfortunately, its perpetual hot starting problem reared its ugly head when they tried to put it on the lift. They got it halfway on the lift, stalled it, and now it won't re crank until it cools down. I'll post when I hear anything from the shop.

n4ynu1010

Ah Ha , scurvy little Pilot bearing , re-start problem sounds interesting

btc50

I'm thinking it's the cold start injector never turning off

n4ynu1010

Yeah the 4 bangers have those bi-metal temperature switches I hear ........................

84sr5yoty

I'm willing to bet that your hot starting problem is related to your timing, which is a mess. I guarantee that your dist is off a tooth, that's what happens when you run out of room for adjustment.

n4ynu1010

Thats very true , you have to be off a tooth or timing way off base setting to be fully to one side of the adj. range on Dist. , and if that is true it would be a bear to start hot especially if too far advanced.