98 Tacoma 2.7 Engine Help

[jp1985]

I am helping my neighbor with his 98 tacoma 4wd with a 2.7l 4cl.
It originally had a dtc code on it. I fixed the ETC and the 02 sensor, and code is now gone.
However it still misses/rough idles, and rumbles at higher speeds.


I checked the plugs,wires,coils,fuel injectors,maf, and none of them had any issues.
We also smoked checked the entire vehicle and no leaks.

The truck was taken into a shop for a blown head gasket before i bought it. They fixed it but am not 100% sure of there work.
My friend said the next thing he recommends is check timing.

Is there any other known issues that could cause this? There is no CEL or Pending codes on it anymore.

Thanks Guys.

JP

 

[tibadoe]

Welcome to the forum.

I would start with the simple and low cost checks first. Definitely have the timing checked first. If it needs any adjustment have it done. Hows the fuel and fuel system? Add a can of seafoam to a full tank and drive it for 15 miles or so. Then as it sits in the tank and lines it will continue to clean and dissolve any build up. It will clean out a fuel system so you can at least rule that part out. Let us know what the results are.

 

[toyotafan]

I am helping my neighbor with his 98 tacoma 4wd with a 2.7l 4cl.
It originally had a dtc code on it. I fixed the ETC and the 02 sensor, and code is now gone.
However it still misses/rough idles, and rumbles at higher speeds.


I checked the plugs,wires,coils,fuel injectors,maf, and none of them had any issues.
We also smoked checked the entire vehicle and no leaks.

The truck was taken into a shop for a blown head gasket before i bought it. They fixed it but am not 100% sure of there work.
My friend said the next thing he recommends is check timing.

Is there any other known issues that could cause this? There is no CEL or Pending codes on it anymore.

Thanks Guys.

JP

How many miles on the engine? More importantly, how many miles since the head gasket was replaced? Do you have more information on what was done? Often the most important thing about a new-to-me used vehicle is how it was used and how well it was maintained and serviced during it's life.

 

[jp1985]

I am helping my neighbor out with his Tacoma since he is a college student and has zero cash to higher a profession mechanic. I am doing this probono he just buys all the parts was our agreement.

Here is the truck info. It is 1998 Tacoma with a extended cab and has the 2.7l engine and has a 5 speed manual 4wd. with only 177k miles on it.

I changed the clutch out on his truck for him so he could drive it again. After working on the clutch
The Check engine light came on.

The engine was running rough, so I coded it. The code was a ECT sensor I forget the exact code #. So I took apart the manifold and replaced the ECT sensor and buttoned everything back up.

The CEL light went away without having to be erased. I thought problem solved and had him drive it around for a few days.

He brought it back to me after a few days and said it has a very rough idle, and it shakes when going 45-55ish. I put a can of sea-foam in the gas tank and had him drive it around a bit. No results it still rough idled.

So I asked him about any recent work done on it before I worked on it, and he told me he had gotten the head gasket replaced, so I am wondering if they did not set it back to correct timing( will be checking that soon). It was done not long before I re did hi clutch for him. Maybe a few months went by and he had the oil changed soon after the head gasket job as advised.

I decided to look into it some more and took the manifold apart to check things out and see if I couldn't find what was wrong.

I then tested the spark plugs and wires they all checked out good. After that I checked the coils where the spark plug wires connect they both turned out to be fine.

The next test I did was a smoke test 2 times and found no vacuum leaks either time that would be causing the engine to be running rough.

While I have the manifold off I cleaned the injectors with sea-foam over night. And sandblasted the upper and lower right side of the manifold to get rid of all the caked on years of burnt oil.

After that I moved onto changing the fuel filter while I still have the manifold off. I just wanted to make sure it wasn't causing a clog. Right now I still have the manifold apart and was looking into some of the sensors. I took off the EGR temperature sensor and the the metal tip that goes into the EGR was completely black.

I am unsure if it is supposed to be that black but when I took a shop towel and cleaned it a bit by just rubbing the towel on it some of the blackness came off and it looked like you could sort of see it was once a different color.

So now I am concerned about the sensors being a cause or part of a cause to this issue, and was wondering based off your list of possible causes this was one of the sensors.

I need to test the rest of them and check timing, but am unsure on how to test the sensors off the vehicle, and could use some advise about that.

I was also wondering if you guys think I am going in the right direction to fix thees issue or should I be doing a different approach.

He needs it back in a week so I have about 7ish days to try and fix this for him.

Thank you all for your time and help.

JP