Hi guys. My 85 se, 2.5L 5 speed, has been idling high, around 15-1700, at normal operating temp since I got it in Feb. I've checked every vacuum hose for cracks, to the point of disconnecting everything but the MAP sensor (won't run without it) and capping off the port. the EGR doesn't have the "accordion tube", it's a cast fixture with the valve perched on top. The exhaust has a slightly rich smell, but it's clear and there is an occasional "pop", backfire style, in the exhaust system. Am I missing something or should I replace the MAP sensor?
map sensor?
- Thread starter bird59
- Start date
Yup. 8 deg before, fat, hot spark. plugs are pretty clean and a little worn but not to the replacement point. It runs smooth, without any misses, no unusual rattles or pinging under load. Nothing. I've also checked the EGR, blocked off the port at the throttle body, with no change. Any other ideas? I'm fresh out!
Well the 4 sensors that can affect idle electronically are the MAP, TPS, O2, and the ECM engine temp sensors.
The easiest way to do this would be to go to an auto zone or a napa and borrow an engine analyzer. This will show you the actual readings from each sensor.
You need to borrow the one that shows all not the small one that just reads codes.
MAP reading wrong vacuum pressure
TPS reading incorrect position of the throttle
O2 Not reading hot enough to go into closed loop mode
ECM temp sensor reading the engine is cold. This will set the cold start parameters (higher idle, richer fuel, not going into closed loop mode) This is not the same sensor used for the gauge/warning light. I have seen a lot of these go bad over the years.
Hope this helps.
The easiest way to do this would be to go to an auto zone or a napa and borrow an engine analyzer. This will show you the actual readings from each sensor.
You need to borrow the one that shows all not the small one that just reads codes.
MAP reading wrong vacuum pressure
TPS reading incorrect position of the throttle
O2 Not reading hot enough to go into closed loop mode
ECM temp sensor reading the engine is cold. This will set the cold start parameters (higher idle, richer fuel, not going into closed loop mode) This is not the same sensor used for the gauge/warning light. I have seen a lot of these go bad over the years.
Hope this helps.
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Yeah, I have a code scanner but I have no codes. Happen to know what the voltage readings should be? I know about the three temp sensors, ECM, gauge/idiot light and fan. I have a feeling that it's either the MAP or ECM temp. thanks for the insight. I'll let you know what I find. Things are moving a little slow, it's been kinda hot. not much enthusiam for leaning over a hot engine... afterthought, cooler weather, cold start rpm around 3000 and drops to 1500 after 30-45 seconds. leans toward ecm temp sensor ok.