Hey guys here is my problem.


I have a 1991 4runner 4x4 with the 3.0 and manual trany with 170xxx miles on it I purchased it a few weeks ago with this problem and have not been able to figure it out.


It is very hard to start and would die almost immediately until I disconnected the vacuum line for the power steering line. It is very slow to rev up and will not go past 3500-4000. There is a strong gas smell from the exhaust as well. The plugs seem to be wet on all the cylinders except for #2.


The engine bay and vehicle appear to have been well maintained and there is no rust. All parts are Toyota parts. No 3rd party stuff. The timing belt was changed at 151xxx miles.




Here is what I have tried so far.

Checked compression by warming up engine as best I could with the way it runs. Pulled all plugs and tested each cylinder. All cylinders were around 90 to 100 but the batter was not the best and nether was the compression tester.


Changed Plugs


Verified spark on all plugs.


Pulled timing cover to verify timing belt had not jumped a tooth and it appears to be 10-4.


One other thing. When you pull plug wire #1 engine dies. When you pull 3 and 5 engine makes no change.


Does this sound like the common head gasket issues or am I missing something else. Any help or ideas are appreciated.

 

check oil and coolant, see if any of the other has mixed ... that would be headgasket. You seem to have other problems otherwise.

 

No oil in coolant and no coolant in oil. Any thoughts on what to check next?

 

Sounds electrical to me. Possible distributor cap and rotor? MAF needs a good cleaning? Air filter needs replacement? O2 sensor, Throttle positioning sensor....

Sent from my iPad using YotaTech

 

Before you throw any more money at it, download a FSM for it.
I would check all the vacuum connections and see if something is crossed or worn out.
Simple stuff first no money spent for diagnosis.
Also check for possible stored codes. Process of elimination. Good Luck
and if you find and fix problem please post it so others can benefit from it.

 

The thing about engine dieing with some plugs removed nit others is interesting. Anyone have light to shed on this? Check timing. It seems this may be related.

 

Hi
i would suspect ht leads are at fault. even though you have vified spark on all plugs they can fail under high compression. what color are your plugs this gives an indcation of how each cylinder is working.
Another thing to try is swap no1 lead with another lead on engine if there is one a similar length. ie remove no1 lead from dizzy and plug and swop.

 

No change when plugs removed on 3 and 5 tells me those cylinders are not firing, but yet you say you have spark on all cylinders. Dying on plug pull on no. 1 and the low tach ceiling suggests ignition timing. Throw a timing light on it, if you dont have a timing light loosen up the distributor and turn it a little bit cw and ccw and see if that makes a difference. The plugs are wet cuz there is no spark on the compression stroke. Ignition timing, bad cap or distributor can cause what you are describing. I just replaced my distributor for a similar problem a while back. When I put the light on it the marker wasnt even on the scale, engine timing was dead nuts. Replaced distributor and life is good again.

 

Knew it was something like that!

 

Lots of opinions on this one!


You just need to systematically check everything that controls fuel or air. Spark issues are usually easy, either the engine will run or it won't. Seeing that you can get it to run, probably not spark.


Check the vacuum connections. Also, check for vacuum leaks by using a can of carb cleaner on a cold engine. Any change in idle means there's a leak. A bad leak would cause the engine to hardly idle which is what you are experiencing.


If not a vacuum leak, proceed to check the VAFM and other fuel and air sensors and components. Don't just replace them, check them per the service manual and if broken, then replace.

 

Thanks for the input guys. I won't be able to work on it again until Monday but i will post check/results then. Feel free to make other suggestions between now and then though.

Thanks

 

So I got 3/4 of the motor put back together from checking the timing belt...and then I pulled the throttle body off to check tps sensor. I believe performed bench checks properlybut was a bit lost when Iit said to pull vacuum in procedures. Could anyone elaborate on this step. I should have a chance to reinstall tomorrow afternoon and would love some clarification before then if possible. Also what should occur when I disconnect tps while engine running. I did this before and it had no effect on motor performance or lack of. Thanks all

 

Don't worry about the vacuum checks, it's not necessary.


If you unplug the TPS it usually idles higher, but that's not necessarily true for everyone's truck. Should also throw a check engine light if it's unplugged.

 

Ok here is where I'm at. The motor is back together and running same as before which is expected because I only verified the timing belt was in alignment. I was able to check compression with a good gage and all cylinders were between 150 and 180. i verified that all cylinders are getting spark. I pulled 3 and 5 wires while engine was running and no change in engine performance. Checked plugs and wires both appear good. I switched a new cap and rotor witch produced no change. Wires are toyota brand and appear new and in good condition.

Going to check distributor next. Any new ideas or thoughts? I don't believe it to be a vacuum issue because of 3 and 5 issues. Both plugs are wet so I tend to dismiss a fuel issue as well. The person I purchased the vehicle stated the issue presented while driving if I recall correctly. I checked the timing and it was off it was at 16 before tdc but I tend to think that has more to do with it being a 4 cylinder at the moment. I did adjust it though to 10 and it did smooth out the idle some but did not effect 3 or 5 and would not start with the timing set at 10 before tdc. Yes I did have the jumper wire installed when setting the timing.

Ideas beyond the dizzy check?

I did check the cold start injector to insure it was not leaking and it wasn't. I have not checked the coolant temp sensor but I did disconnect it to see if any change would occur, none did. To be honest I didn't expect a change but you never know. Also checks were conducted with tps connected and disconnected, same results

 

Can you elaborate on how to check for the vacuum leak with carb cleaner. I'm not familiar with this and it's kind of looking like this could be an issue. Would love to confirm before pulling intake off. Thanks

 

Yeah, this guy explains it best:

 

Thanks, Your right he explained it well. I'll give that a try Monday hopefully.

 

Seems like a big variance on compression readings from 150 to 180 psi.
30 psi difference, should be no more than about 14 psi difference.
Do you have the readings for each cylinder # that you can post up?
Possible there is a problem at #3 or 5 or both.

 

Yeah your right the way I posted it was a bit vague. I didn't keep track of what cylinder had what psi but they were all very close I just quoted the specs in my post.

 

I have found my problem...
I took the intake off pulled the fuel rail off and discovered some less than ideal stuff in the #3 fuel injector fuel rail hole. The #3 and #5 injector had deposits from the same. Guess I need to give the entire fuel system from the fuel tank forward a good cleaning.