Jump to content

Another #$%@ problem

Recommended Posts

Now that I've spent about $700 to fix the A/C, the engine is running poorly and I'm stuck driving my old Toyota in 90 degree heat. At higher speeds the engine is slightly missing, making it pretty jumpy at highway speeds. It doesn't do it in first and second gear, and doesn't seem to be as bad if I'm really giving it the throttle. Fifth gear is the worst. (By the way, this is a 95 K1500 W/T V6)


It seemed like a fuel problem so I replaced the filter, which didn't help. I figure it isn't the pump since I can rev it up to 3500 in the driveway and it seems fine (also fine in 1st and 2nd gear, too). It starts great and idles fine, and driving in town seems OK too. All the ignition parts are new within the last year, so I doubt it's a spark problem.


Someone suggested vacuum leak, but wouldn't that set off the check engine light? It hasn't come on. I noticed that changing the airflow on the HVAC controls takes a reeeal long time to change, and that's vacuum controlled. If you have any suggestions please let me know...



Link to comment
Share on other sites

That engine should have a Throttle Body Injection unit If I remember correctly. They were known for vacuum leaks at the TBI base gasket or the intake manifold gasket, or both....It may have been leaking before you had the A/C work done, you just notice it more with the extra load of the A/C compressor.

It is also possible that the guy doin the A/C work may have knocked a vacuum line loose or even cracked one of the plastic vacuum lines. A vacuum leak will not always set a code that turns on the CHECK ENGINE light.

I would suggest that you do a visual check to make sure that everything is in place first, then you can use a can of carb cleaner and spray a little around the base of the TBI unit, if the idle increases then the base gasket may be bad. If that appears to be OK then pull the PCV valve out of the valve cover and place your thumb over the grommet in the valve cover while the engine is running, I've seen the intake gaket fail causing a vacuum leak in the crankcase, if this is so, then you will feel slight sucktion on your thumb....

I would also check the base ignition timing. If it is too far advanced it would cause a pre-igntition condition and cause the ECM to retard the timing to keep it from pinging, which will also degrade performance.....


These are a few things that I would check....GOOD LUCK!

Link to comment
Share on other sites

Have you done a tune-up lately?

My '95 needs a new cap and rotor once a year. It gets all corroded inside. I usually get a miss at about 2500 rpm.





Funny you should mention that. Took it back to the guy who did the A/C and he drove it and said "definitely ignition." Never would have guessed that since it starts and idles fine. I checked the plugs and sure enough one was covered in gray/brown soot. I replaced the plugs and wires and the problem went away. Wonder what caused it?


Thanks for the other suggestions. I understand the intake manifold problem well--I did that last year.

Link to comment
Share on other sites

If your plug is grey, it's running lean. Plugs should be a nice tan/brown color.


Have you done a compression check?

My 95 started missing badly on long uphill roads when I was loaded down and needed all the power I could get. Did the standard tune-up and fuel filter change - no help. Did a compression check, cylinder #8 had only 75 lbs of compression. This was at 62,000 miles! All the others were good. The plug was lean and oil fouled.

To the dealer I go (thank God for the extended warranty), after their checks, they were able to determine that cylinder #8 was out of round. The shop manager said that he had never seen that before.

So under long, hard acceleration, all the oil was being sucked out that cylinder, going by the 02 sensor and leaning out my fuel ratio. It would just starve for gas.

So I got a new long block for $53.75 and a rental for a week.

So now I have a 123,000 mile truck with a 60,000 mile engine.

(Oh, and a dented hood and passenger front fender when a tree fell on it.)

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.