Rough engine

[wemtd]

Gentlemen

 

Now that cold weather has arrived an odd engine problem developed when out for a recent evening blat (~30 F), not wanting to run above 3200 rpm.

 

This started shortly after startup and lasting beyond coolant temp reaching running temp, but resolved ~30 minutes later.

Beyond 3200 RPM the engine/ECU jumps to thinking the engine is at 16,000 rpm. After the rpm spike the speed drops (I suspect the rev-limiter is activated until the ecu thinks the engine has slowed down and the engine re-engages). This cycle continues if i maintain the throttle position: there is a loss of power and the RPM fluctuates between too fast and too slow. If i let up on the accelerator to re-establish an RPM below 3K everything is normal until i reach 3200 again (regardless of whether i do so quickly or gradually).

Once well beyond full warmup this problem goes away.

 

I don't think the issue is with the sensors because they both give similar voltage readings with data logging and think it less likely both would go bad at the same time. The fact that this issue resolves AFTER warm up leads me to believe it is not likely related to the air temp/coolant temp correction tables in the ECU setup.

 

I am not sure if this issue is caused by a deficiency in my engine tune, cam/crank shaft sensor error, or wiring harness/connection/ground error?

I suspect there must be a slightly off connection in the harness resolving once everything beneath the bonnet is hot. Any ideas (other than every connection) as to likely places to check?

 

Duratec 2L Birkin, Haltech Sport 1000 ECU, ITBs, street use only

 

 

Cheers

P.

[bsimon]

Clapped out TPS maybe? Have you watched the TPS track in data logging?

 

If your ITBs are Jenvey, they will have a Colvern TPS. This particular model is known to shoot craps. I've been through two Colverns before swapping to Bosch part from a BMW 328.

[BusaNostra]

Lot's of variable there.. if you think it's not any of the sensors? But if any of the sensor is bad, it will throw you out of loop.

You said, it resolved after it warms up and only happened now... winter cold? Then, that can't be a wiring issue nor the value of the mapping on cold start, unless you change the value. I'm still leaning toward the coolant temp sensor. This sensor is the most important to the ecu during cold and hot start up. Coolant temp sensor will send signal to the Ecu, instruct the thermotime switch (cold start injector) to push more fuel less air (sort of choke in the old system). If the cold start injector or the coolant temp sensor are not functioning during cold start, the car runs rough....engine needs to get hot to reach the proper tolerance.

 

Check both....

Edited November 22, 2012 by BusaNostra