QuestionHave checked the lines to the turbo but will double-check. What's troubling me is that it idles perfectly until it warms up. Then it consistently gets a rough idle, engine miss and the buzzing noise in the dash. It runs greatfor consistently for the first few minutes until it warms up. Also, even when it is warm and having idle speed problems, it accelerates great under hard acceleration (and boost guage seems to work fine). Again, all the symptoms start consistently when the car comes up to temperature, NOT when started cold! That's why I was thinking that the air flow sensor, TPS, fuel pump and fuel regulator were all OK.... what do you think? Thanks!
J.C.
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Followup To
Question -
1987 760 Turbo 4cyl. with 89K miles. (Recent work was a new cap, rotor and wires (plugs are fine). Car has generally running fine (for about 500 miles after the above work) but at cold start, car would stall twice and then start and run fine. Just replaced the battery and alternator. Immediately afterward, car began idling rough when started and stuttered/missed when driven. Re-checked cap, rotor, wires, plugs, vacuum lines, throttle body (was clean) and air filter (clean). I must have fixed one connection problem because car now consistently runs good when started cold (does NOT stall anymore) and runs good for first few minutes. When it warms, idle is very rough (rich mix, black smoke), engine misses at lower speeds and at shift points. However, engine runs fine under heavy acceleration. At, steady higher revs (above 2K), the engine seems to run better. In addition, an odd whine/whistle (angry bee) sound has begun and seems to be coming from the upper driver dash area, behind the console or headlight switch when the engine is running roughly. FYI, disconnecting the air flow sensor and engine coolant temperature sensor (not the dash indicator but the computer sensor on the plug-wire side) did NOT make any difference. What do you think is going on? Thanks!
Answer -
Jerome,
Black smoke and rough idle, look at the fuel pressure and check all the intercooler hoses making sure they are tight and not leaking under boost pressure. Fuel pressure sometimes drops, weak pump or bad regulator. Also at times they rupture and leak fuel through the vacuum line into the engine. That makes them idle poorly. Test the O2 sensor and see that it is working, may be shorted out and causing a rich mixture. Mass air flow sensors often go out and act very strangely, you may have to try a know good one if none of the above things are wrong.
The noise behind the dash is possibly the boost pressure line to the gauge, perhaps it has come loose or the line has broken. At idle it has vacuum and under boost that changes to pressure.
AnswerJerome,
The buzzing noise in the dash, do you think that maybe following that as it warms up could leed to something? I really can not amagine that it will, but all the problems occure when the noise starts. Also there is a fuel injection temp sensor rear of the head two wires that as the engine warms it send its signal to the control unit. Have the sensor tested or replace it and see if that helps. As the cars warms up the signal from the O2 sensor begins to control the fuel mixture, if you unplug the O2 does it smooth out? What is the fuel pressure at during this time? Is the pressure regulator possibly leaking through the vacuum line, or holding the pressure to high or low? Is the buzzing possibly from the main fuel pump? Caused by it starving for fuel because of the feed pump not working.
