Strange cold temp issue

[mandkole]

Hey all lend me your ear... it's been cold in the pnw and had a strange run issue from months ago in spring repeat itself today. The motor had cold soaked down to about 20f the last few days. Was a hard smoky start (not plugged in),hopped in and drove my mile to the highway then travelled about 10 miles and exited. EOT only got to 150f or so. As I got off the highway, noticed some unusual haze and pulled into fuel station. The white fuel smoke became heavy, but no knock, yet the motor was quieter like the timing was pulled. I checked the CCV tube and all good but noticed the PW was high at no load idle (1.5-1.6ms). Shut it off.

I restarted it, the pw went to 1.3 (normal), the normal cackle came back and the pipe was clean. ICP and dc were normal and ran fine rest of day. What the frack?

At this time I plan to change both the EOT and icp sensors to rule them out.. The EOT is about 50f high when cold and the icp has had oil in it. Could these drive a weird fueling issue?

 

[ghohouston]

Im pretty sure timing is somewhat calculated by eot. Icp sensor obviously can cause all sorts of wacky issues.

 

[TyCorr]

My truck has done that a few times...dont worry until.it sets a CEL.

 

[mandkole]

My truck has done that a few times...dont worry until.it sets a CEL.

Yeah no cel. I hadn't looked in the scan gauge yet to see if a cel is in there. Still plan to order up some sensors for grins. The EOT does control cold start timing and a failed one defaults to 70f or so. It's never aligned with the trans temp when cold.

 

[TyCorr]

I also have a cchitted up oil pressure sensor and it seems to do all kinds of whacky shti to idle and such.

 

[mandkole]

Could be.. like we've all talked before, sensor issues can create all kinds of problems for these damn things. Light switch-like changes are just frustrating. I wondered at one point if it was the chip, but its been so infrequent/random that I forget about it until it comes back.

 

[HEUIGuy]

There is a Pulsewidth multiplier the is a function of ICP/EOT. And there is also a SOI map With the same normalizers.

If the EOT sensor is not sending a consistent signal it could very well increase/decrease PW and SOI based on the maps.

Are you monitoring EOT through the PCM?

 

[mandkole]

I was wondering how the modifiers interacted with the sensor voltage. It would seem that if they are wrong, it could be an issue and may explain why the idle completely changed with shutting off and restarting.

The EOT is coming from PCM through the scan gauge. I can pretty well know what ambient is with the trans temp, but the EOT has always been about 25-45F higher than ambient when cold. The colder it is, the farther its apart. It pretty much doesn't track ambient at all.

 

[HEUIGuy]

Did your EOT readout change between when it was running and you re-started?

The changes in those maps are dependant %100 on how your tuner calibrated them.

 

[mandkole]

EOT was not seen because it was not pulled up on the gauge at the moment of the observation ( you can only see two parameters at a time)... The thing I correlated was a heavy fuel smoke 1.6ms with a more 'hushed' tone, to shutting it off, restarting and showing 1.2-1.3ms, hearing a slightly louder cackle tone with zero smoke after the pipe was cleared out.

The goofy 'whisper/drive thru' file on the chip will smoke exactly the same way, but it is real quiet with zero cackle.

 

[thatdude]

10 minutes isn't enough to get upto temp. Drive it an hour and tell us what it does then. If it's normal, than call it good.

 

[mandkole]

10 minutes isn't enough to get upto temp. Drive it an hour and tell us what it does then. If it's normal, than call it good.

Id agree that less than 160F is not warm enough. But, that isn't the issue in this case. Turning the truck off, then on, with its behavior changing is my concern.

 

[golfer]

could have been a sticky IPR valve...(or anything else that could lower ICP)

for a given MFD, if ICP pressure is low(er than normal)< hence the quieter engine tone, then the only way the PCM can reach the desired MFD is to increase inj PW

 

[mandkole]

could have been a sticky IPR valve...(or anything else that could lower ICP)

for a given MFD, if ICP pressure is low(er than normal)< hence the quieter engine tone, then the only way the PCM can reach the desired MFD is to increase inj PW

interesting-- I suppose that the IPR could be sticking and it helpful to understand what the PCM wants to do. I also know that Ive had an oily ICP sensor for awhile now and planning to change that. This is such a random issue and the last time it happened, it was also much warmer than 25F.

 

[mandkole]

Update--swapped the sensors yesterday. The ICP sensor must have been giving it up as the motor is butter smooth now at all oil temps. More responsive throttle and a lot more tip in fuel at same PW. The EOT sensor wires were rubbing on the fuel line block and showing minor damage but the sensor did not produce any change in Pcm based temp reading.

Still no indication of reason for the original issue.

 

[superpsd]

The whisper mode is just adjustment to lower the base idle speed and retarded global timing.

 

[mandkole]

Yes, 'retarded' represents what my whisper tune really is... theres no way Id ever use it. Its not even close to being usable with larger nozzles.

 

[mandkole]

chip issue??

To update this, it just did it again on a cold start today. Muffled cackle and heavy smoke. It sounded just like the whisper file. After 3 starts doing the same thing, I flipped through all the chip settings and no change. I could start the truck on the no start position. Same whisper idle-- the switch did nothing.

Removed the chip, reinstalled and restarted, it was back to normal.

Could be a bad switch, failing chip, bad connection on pcm?

 

[Arisley]

Sounds like a dirty connection on the chip and or PCM.

 

[mandkole]

Yeah, I'm answering my own questions, but was curious if the switch is any more prone to failure than the other parts. The chip connection would appear more fragile than the switch. I suspect the switch is fine after it worked correctly in all positions after reinstall.

It's an excuse for a hydra lol