Matt96Tacoma

Hello and thanks in advance for any help that can be provided.

1996 Tacoma Xtra Cab 4x4
4 cylinder 2.7 liter

My truck has been starting fine but my gas mileage has been very poor over the last 6-8 months. I have tried cleaning the air filter, oil change and tire pressure but nothing has worked. I decided to replace the spark plugs, spark plug wires, oil, oil filter, pcv valve, distributer cap, and rotar and charged K&N air filter. I put the wires on just as they came off and I have never had any problems changing plugs/wires with other vehicles in the past.

Once everything was installed I tried to start the truck and it cranks over but does not start. I triple checked the firing order and everything is correct. Counter clockwise 1,3,4,2. I pulled the plug and confirmed that I was getting a spark. After going over everything and not finding the answer I decided to put on the old distributer cap and old rotor. It still did not start. I pulled all the new NGK plugs and put in the old Bosch plugs and wires and again no luck.

I decided to pull all the old off and put all the new back on. Once everything was back on I checked the MAF sensor to see if it looked dirty. I am getting NO CODES or CHECK ENGINE light. The sensor looks fine and I cleaned with the correct electronic cleaner as I have done in the past. The truck still would not start. I decided to pump the gas peddle over and over and it started and then quickly died. I decided to pull the air filter thinking maybe I put too much oil and maybe it was starving for air? It still would not start. After messing with it for hours it finally started and it stayed running only when I keep pressure on the gas. Once I let off it will die. I decided to get a fuel filter thinking it might be a fuel issue? After installing I am left with the same result. I have tried to start by removing or bypassing the Intake Air Temperature sensor in the air box. Once I did this the Check engine light flagged of course and gave me the IAT code. I removed battery lead and cleared the code and connected the sensor. I feathered the gas and after hours I was able to start the truck and I raised the rpm and let it run for about 10 minutes. During this 10 minutes the timing seems fine. As soon as I left off the gas it dies and sometimes will backfire out of the air intake line/box. It is a white smoke that comes out. When I put the ignition to ON I do not hear the gas pump but I never did in the past. I am not sure if this is a fuel issue, vacuum issue, or sensor etc. I would think that the system would flag a CODE if a sensor was bad?

I have since pulled the fuel pump and tested the resistance with multileter. It reads 1.5 ohms. The manual shows .2 - 3.0 ohms. I also jumped it with 12v directly off the battery and it pumps.

Strange part.....
After putting the pump back it would not start. I decided to undo the flange in front of the catalytic converter and tried to start. I tried about three time for about 5-7 seconds. On the 4th try it fired right away and idled on it own. I was shocked and puzzled? Could I have a completely blocked catalytic converter? I turned the truck off and started it again. It started right away with no issues. I called a local muffler shop and he said for me to come right over and would cost $200 for a new one. He told me that in 35 years he has never seen a vehicle not start due to a catalytic converter and he said for me to bring it and he would not charge me if the exisiting one is not bad. I said great and started across town. Of course it started raining really hard and once I was about half way there the truck died. ( I was driving the entire time with open exhaust). I had it towed back to my house and just picked up a fuel pressure regulator. After reading the manul my model 2.7 liter is not listed in the back of the book. It does show the 2.4 model. I was going to hook up to the fuel rail and see what the pressure is.

The only other thought is perhaps bad gas? My wife purchased the gas 2 days before I changed everything (plugs, wires, etc.) It ran fine before but we have been getting a ton of rain over the week she filled up. Perhaps rain water got in the Underground tanks at the station and I have a lot of water in my tanks?

I will dreain the tank and put a gallon of fresh gas tomorrow but just thought I would post on this site and see if anyone has any ideas or suggestions...

I also have checked the Throttle Positioning Sensor and according to the ohm meter it is okay?

Also all the fuses and relays (efi) have been checked and they are also good...

I have also replaced the battery due to draining it many times trying to start and making sure it has enough voltage. Brand new Napa optimum..

Still no CHECK ENGINE LIGHT?


Thanks in advance..
Matt

toyotabull

So it will run with open exhaust, but you have to feather the pedal to keep it running with the exhaust back on? No codes? Ok, bad gas, clogged catalitic maybe, unusual. Check your pressure on the fuel and hopefully someone on here will be a better help than I am

Matt96Tacoma

Thanks for the reply...

I know it is a very weird one.. Usually there is a code to reference and a solution. In this case I am troubleshooting over and over in different areas. If it was the exhaust you would think I would get a 02 sensor flag before or after the converter. I am not too sure now that is it? I think with some OBD2 scanners it can check the fuel pump to see if it is okay. (votage wise and if pumping) The only way to check the pressure is the fuel rail with the regulator. I will post back the pressure results...

Thanks,
Matt

Matt96Tacoma

I have been so busy working on this I haven't been back to post my findings...

I checked the fuel pressure and it was fine at 65 pounds before the fuel rail. After calling around and asking more and more questions a mechanic suggested for me to check the compression..

Compression results:
Cy1 = 170lbs
Cy2 = 160lbs
Cy3 = 160lbs
Cy4 = 175lbs

Seems to have good compression...

eddieleephd

Compression looks ok... I would suggest replacing the cat and see what happens, after clearing the ECM the way you did I can see why it has not thrown a code. Basically if there is no outlet there will be nothing coming in at least not enough for the ECM to give fuel which sounds like your issue...
It does make sense a screwy way to find this issue but not unlikely...

So yeah go and do the cat and maybe the O2 sensors for good measure and this should fix your issue. Remember if the front O2 sensor is too dirty the ECM may not have sufficient numbers to say the CAT is clogged, so yeah I would say both O2 sensors and the cat should do...Since what you are saying makes sense that way.

if you clear your ECM Memory it has to relearn every thing.....if you really want to test this theory you can pull the cat off tap with pipe or hammer and knock as much gunk out of it as possible use some gas maybe to help clean it out and reinstall... however The Old Man sitting next to me is in agreement and has seen this specific issue cause the same problem in the past...

remember the old cat is worth a good bit of money do not just give it away take it to a recycler!! and get the money for it.....

Matt96Tacoma

Spoke with another tech and he suggested I look at the valves since it will run with open exhaust frequently.
Purchased a feeler gauge and the exhaust reading was supposed to be .010 - .014
My results:
Valve 1 =.08
Valve 2 =.07
Valve 3 =.08
Valve 4 =.06
Valve 5 =.08
Valve 6 =.08
Valve 7 =.07
Valve 8 =.08
After doing research I found out that there is Valve Shims. I pulled the CAM and removed the shims. All of these measured .113 inches / 2.85 metric

Matt96Tacoma

Next I purchased the new valve shims from dealer and replaced...
Since it would take 2 days to get I decided to clean some parts..
I cleaned the EGR VALVE and also the throttle body.

eddieleephd

due to your last post would suggest both doing the valve shims and cat... even stronger thought on a top end job where you get the valves reseated and should hum really nice....

Matt96Tacoma

Once I recieved the shims I installed and it started right up. It idled with no problems with the CAT disconnected. There was NO TIMING issues. Idled perfectly....
I drove to the muffler shop and purchased the NEW CAT...
On the drive home it started sputtering... I could not beleive it!
I decided to continue to drive and HOPE FOR A CHECK ENGINE LIGHT! I drove for 30 minutes sputtering really bad. It will sputter more going from 1st into second at LOW RPM.. Still no check engine light I decided to take it into 4th and sure enough on the Main Street going 55mph it started sputtering heavy and completely died... I was towed back and it was the same tow guy as before... I am looking like a real idiot...

Matt96Tacoma

Thanks for the reply Eddie... We are both replying at the same time...

Matt96Tacoma

So once back to me house... I checked the basics again...

Pulled Cy1 wire and put plug and grounded against the moter and NO SPARK?

Matt96Tacoma

I pulled the Ingition Module and took it to Autozone and Napa and had it tested. Still no Check Engine Light and it PASSED all tests...

Matt96Tacoma

I pulled the coil from the distributer and it is reading Primary .8 and secondary 12.7 so according to the manual it is good. I called the Tech at Toyota and he said the magnets in the distributer go out on these trucks. I am soooo tired of troubleshooting this...
Is there a way to test voltage/resistance on the distributer itself and not the coil? IS it true about the magnets going out on this model? Any thoughts and advice are appreciated. I just order the new distributor $255.00 and I can return it if I do not install.

eddieleephd

check the voltage coming out of the alternator look for about 13.6v any thing over 12.5 should work but if at 12.5 or lower new alternator is recommended,
as for the distributor no the spark comes from the coil through the distributor best you can do is a visual inspection... check your fuel pressure again...

eddieleephd

what about O2 sensors did you replace those??? and the vaf maf sensor???

Matt96Tacoma

MAF sensors is good. I cleaned it and no check engine light.

The 02 sensors and also good...

Still no check engine light? Why would the alternator voltage play a part in this?? I will check the voltage.. Do I check with the ignition ON or OFF? Also I tried crannking the motor and pulled the distributor cap off and see week spark coming off the Rotor...

eddieleephd

did you ever drain the tank for water you can pull a plug if there is one and if gas comes out first just put the plug back it should be good if water is present then drain water till you get to gas...can do this with a syphon hose and same as long as the hose starts on the bottom of the tank...
I am leaning towards the sensors and the water thought at the moment..did you look at the fsm??

Remember the first thing the ECM looks for is intake and TDC via the coils in the bottom of the distributor...

suggest first look for water in the fuel then the sensors if no water present... if the ECM is not seeing appropriate induction it will not give fuel or spark...if it does not give fuel it will not give spark and vise versa...I know this is annoying and I am trying to point you in the right direction...What other sensors are there on your model??? did you ever check the timing belt???

eddieleephd

Did you have the maf tested how about the O2 sensors how do you know for sure that they are good??? you cleared the ECM and it runs on a three trip system the issue has to be recognized three times to trip the light!!!
Alternator not putting enough voltage out can cause a weak spark..the battery is just there for starting purposes and with a weak alternator will drop battery voltage..will acquire a charge while sitting...

alternator is checked with the truck running,,, mine does not go above 13.6 yours may go to 16...

eddieleephd

PM'd you call me in a minute or respond with a number and I will call you...

Matt96Tacoma

I see...

I will check the voltage with the ignition ON and see what it is at? I did pump 1 gallon of fuel out when I did the fuel pressure test. No water was present...

In regards to the MAF/VAF I cleaned with the Electronic cleaner and when I pull the wiring harness off I get a Check Engine Light. I reset etc.. I think it is working fine...
I also will get a check engine light if I pull the 02 sensor off etc..