QuestionQUESTION: This just started about a week ago. The car has approx. 52,000 miles on the v6 and has been kept in great shape. If I keep a very slow acceleration, it will get up to speed, but if I do what could be considered a normal acceleration, it will hesitate and "cough and sputter" but eventually get up to speed. I have some "shade tree" type of mechanical experience, so depending on the severity of the problem would like to fix it myself. Thank you ahead of time for taking the time to help me with this problem. I do appreciate it!
ANSWER: Hi Rob,
It is probably a mixture problem but to start you could check for fault codes using the ignition switch:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light, which remains 'on', to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to be sure of a repeatable set of count numbers. Group the counts in pairs to form the two-digit fault codes. The last code is always 55 which means 'end of readout'. Let me know the other codes or go to www.allpar.com/fix/codes.html for a code translation.
A possible cause, which may not show up as a fault code is the egr valve being sticky in its action and in fact sticking slightly ajar which leans out the mixture too much for acceleration conditions. The valve is located near the throttle body air intake at the end of the engine, mounted in pipe that recirculates exhaust gas from the rear cylider bank exhaust pipe back around to the intake manifold. The exhaust gases have some fumes that can plate out a crud on the valve stem and thus keep it from closing tight when you are at idle. That makes for a too lean mixture so the engine stalls. The valve proper is mounted horizontally with the stem visible in a space between the body of the valve mounted on the pipe and the round top of the valve which is flanged and so if you look carefully you will see a metal rod (stem of the valve) with a slot around its circumference. You can take the tip of flat blade screwdriver and insert it in the slot and then lever the valve back and forth to check if it is moving freely (against spring action in one direction) or not. If it doesn't seem to close easily with the help of the built-in spring, then I would spray the base of the stem with solvent from a pressure can (such as WD-40 or carb cleaner) while moving the stem back and forth. Then see if that solves the issue.
The last suggestion would be to clean the throat, both sides of the butterfly valve plate, and side idle air passage of the throttle body, using a solvent to remove crud build-up. That too can affect mixture.
I think one of these approaches will bear fruit.
Roland
---------- FOLLOW-UP ----------
QUESTION: Thanks for the quick response. I ran through the codes at lunch and it was just a 12 and a 55. I hadn't disconnected the battery, so I am assuming that is an old code, but you would be able to answer that much better than I. I didn't have much time, but could not find the egr valve or a pipe running from the rear cylinder bank exhaust anywhere except the one that connects to the front cylinder bank exhaust, which was at the drivers side, or back side of the motor. If it makes any difference, it is a 1991 3.3 V6, and I apologize for not giving you that information before. I'm sure I was just not looking in the right spot, so if you can, maybe give me a better idea of what to look for, if that is possible. Does it come in from the bottom, top or side of the intake? What size of pipe should I be looking for? I am used to the old carb type that just led right up to the air cleaner, so that is probably why I am missing it. Anyway, any other help that you can give me would be greatly appreciated. Thanks again!
AnswerHi Rob,
You are correct in that the 3.3L doesn't have an egr in '91 except if sold first in California, but all the 3.8L engines (nationwide) do have the egr. I checked the 3.8 underhood sticker and assumed it also applied to the 3.3L, not thinking that you may have a 3.3, so should have looked at that sticker too.
So try cleaning out the throttle body throat and see if that has any effect. It would be worth also checking the pcv valve and hoses for a possible leak that would lean out the mixture. Check vacuum hoses associated with the intake manifold for a crack or disconnect. After that, fuel pressure may be worth a measurement, which should be around 48 psi. There is a service port on the fuel rail to which a gauge can be connected.
Roland
