Newbie C4 1990 ROUGH RUNNING
Thread Starter
Intermediate
Joined: Nov 2014
Posts: 49
Likes: 3
Newbie C4 1990 ROUGH RUNNING
Greetings from Sunny London!
Picked up my new C4 last night which has a running issue. The car is a low mileage 27600 miles from new. It's starts up fine and runs ok when cold but not 100% and once warm it runs extremely lumpy up and down, dropping power, popping through the exhaust, a bit like if the choke is staying on (doesn't cut out). I have to manipulate the throttle to keep her moving at speeds of 50mph +.
Could it be EGR sensor or TPS sensor?
Picked up my new C4 last night which has a running issue. The car is a low mileage 27600 miles from new. It's starts up fine and runs ok when cold but not 100% and once warm it runs extremely lumpy up and down, dropping power, popping through the exhaust, a bit like if the choke is staying on (doesn't cut out). I have to manipulate the throttle to keep her moving at speeds of 50mph +.
Could it be EGR sensor or TPS sensor?
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
It's in open loop, meaning no sensor input until warm, when it enters closed loop operation, using all sensors.
Check proper vacuum, too; steady at around 19-22 or so. The ECM, seeing lean due to unmetered air, makes it add fuel (run rich).
The basics of any engine applies: proper fuel, spark, and no extraneous air.
Check proper vacuum, too; steady at around 19-22 or so. The ECM, seeing lean due to unmetered air, makes it add fuel (run rich).
The basics of any engine applies: proper fuel, spark, and no extraneous air.
Last edited by whalepirot; Nov 18, 2014 at 12:02 AM.
Cruising
Joined: Nov 2014
Posts: 12
Likes: 0
i dont know if this applies to a later model, but i know the earlier models have problems with tired fuel pumps. i would give it a tune up, judging by it's miledge it has sat for most of its life. spark plugs, oil change, fuel filter, air filter, wires. my 84 would stall randomly at idle because of old spark plug wires...
Last edited by vejayel; Nov 18, 2014 at 12:03 AM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The only difference between open loop mode and closed loop mode is that the ECM uses the O2 sensor in closed loop mode. That's because the O2 sensor is useless until it gets up to operating temperature. All other sensors are used while in open loop mode.
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