1999 Toyota 4Runner

Engine Performance problem
1999 Toyota 4Runner 6 cyl Two Wheel Drive Automatic 138, 00 miles


We have an intermittent problem that only occurs sometimes when the car first starts. It runs rough and then smooths out and runs fine after 2-3 minutes. It seems to only occur if we have previously driven the car that day. Sometimes when we start it and it runs rough just turning off the car and starting it up again can fix the problem. Sometimes we have to drive it for 2-3 minutes for it to smooth out. The problem has not yet occurred at the first start up of the day. The engine light has only come on once and went off after the engine smoothed out. The repair shop cannot find anything on the computer during diagnostics. We asked them to replace the spark plugs, spark plug wires, fuel filter and air filter and they argue that those parts are not due to be replaced (especially the " lifetime fuel filter" ) and don't want to start replace parts until they can find the problem.

We have taken the car to the repair shop twice now and they cannot duplicate the problem. They have run all kinds of tests and say the car runs great.

Have you seen this before? Is it something we should just learn to live with or could this be causing damage to the engine to run it while it is running rough?
September 11, 2009.

THe problem with this type of problem is without a code, everythng is a guess. I'm glad to hear that the shop doesn't want to just replace parts until they find the problem.

If I had to guess at this point, I would say the temp sensor or the EGR may be the problem. However, have they checked fuel pump pressure?


Thanks so much for your reply.

The repair shop was finally able to duplicate the problem and saw the engine running rough for no longer than 5 seconds and then it smoothed out again. They described it as if it weren't firing on all cylinders. In the process of removing and replacing the spark plugs to check their condition the spark plug wires fell apart. I guess they were after market wires and were in bad shape. They had to replace them and now we are just waiting to see if that fixed the problem or if there is something else wrong.

If we see the problem again I will let you know. Hopefully you won't have to hear from me again. : )

Thanks again!

Sep 13, 2009.
I'm glad you found the problem. If you have questions in the future, let us know.



The spark plug wires did not fix the problem. It is still running rough intermittently. I called the repair shop to ask if they had tested the fuel pump pressure and they said that the car was not running rough long enough for them to check the fuel pump pressure. I also inquired about possible temp sensor and EGR and again he said that he did not get a chance to check those things while it was running rough and that we need to bring it back and have them perform those tests while it is acting up. He said that the engine light went on for a second and all it showed was multiple misfirings. He said that they suspect either fuel injector or ignition coil but since they don't know which one is failing they would have to replace them all to fix the problem and that could be pretty expensive.
Does this sound right to you? We have a road trip coming up soon and we were hoping to find the problem before this. All we know to do now is to try to drive as much as possible near this repair shop to try to get it to them while it is running rough but that is a difficult thing to do.

Thanks for your help!

Sep 17, 2009.
Either could be the problem, but why replace everything that is good hoping to find the problem. If they feel they need to have it running rough, all you can do is hope it happens when it is near the shop.