Now that the warmer weather is upon us here in the Phoenix area I have once again a reappearing mystery.

When my car hits an oil temperature of 200* or so it seems to run slightly rough. The exhaust gets a bit louder as well. It's not skipping but the car just doesn't feel as smooth and crisp as it does when it's cooler. During the winter months I don't experience this when the oil temp is below 200* and AC isn't necessary.

I run a 160* thermostat so the water temp doesn't exceed much past 190* on a 110* day with the air on even though the oil temp will be 214* while cruzing at 75mph. Oil temp will drop 5* while driving slower thru town.

Logging with my tuning software my fuel trims are right on the money, spark is right where it should be. Wideband shows AFR to be right where it's commanded to be when the car starts it's "not smooth" thing.

It's annoying and I can't for the life of me figure out what could be doing this. A friends car did a similar thing. He has a similar cam but more compression. When he added a Dewitts rad/engine oil cooler his problem went away since his engine oil temp stays in the 190's.

Yes I could add an oil cooler as well but there must be an explainable reason to why the car runs slightly rough when heated up. I know guys that run much higher oil temps then mine.

I would first suspect vacuum in the gas tank or something happening the fuel in the lines when the car gets hot but my tuning software tells me things are fine???

Anyone else experience this? I could sure use some input here.
Thanks Guys.

 

Second fan probably kicks on is what you feel.

 

I don't believe the fans run at speeds over 35mph, at least my "fan 1" setting from GM is set to turn off at 35. I believe "fan 2" would not run if "fan 1" is off. Please correct me if I'm wrong and thanks for the thought.

I still would guess it's a hot fuel issue? I wonder if a return line to the tank like the early C5's had would keep the fuel cooler and fix the problem???

Don't forget that I mentioned that the exhaust note changing was the second symptom.
Funny, when my friend and I were cruzing on the freeway, when this stuff started to act up, he would call me on his cell and tell me to pull up to his rear quarter and roll my window down to see if I could hear the change in sound of his exhaust. He always thought it sounded like a motorboat when this happened. Well with his extra loud Borla Stingers I could sure hear his car at freeway speeds with my window up! But with the window down I could easily tell his car also sounded wierd and like a motorboat! Keep in mind this is just cruzing at 70mph. But when he put it to the floor it's the normal "blow out your eardrum loud! So we nicknamed the symptom "motorboating". Mine is much quieter but the exhaust pitch does change. Freeking wierd!

 

Is it mainly an Idle issue or do you feel it thru all aspects of driving?

There are some "ASSOCIATED" tables that influence some of the main tables that may not be properly modified.

For instance; (My heads cam, fast 90/90 02 ZO6) After the heads cam install I had an IDLE problem any time I turned the AC "ON".
The idle would surge up and down and the engine would DIE.

ENGLANDGREEN adjusted a aecondary idle table that added or subtracted timing when the AC is on. The issue was that the values in each table were so different that the PCM would jump to the AC Timing table and the timing would be too low and the engine and it would die. He matched up the two tables for timing to support AC operation at idle and PROBLEM SOLVED.

Easy fix for a tuner that KNOWS what all the tables do and how they react and relate to each other.

For me it was a DAMN NIGHTMARE!!

So, saying all of that,,, look for an oil temp related table or a table that effects timing when the engine oil reaches that level (if there is one) or something that changes in respect to oil temp that isn’t proper for your modified engine / PCM parameters. If the exhaust sounds different, it most likely a change in timing that changes the exhaust note.

I’m not tune savvy so don’t ask me what table/s they are. I understand it all and the relationships but,, changing those tables to the CORRECT value, isn’t my thing.

Hope this helps.

BC

 

Thanks for your thoughts Bill. I wish this was an electrical problem. Then I know you would know the answer!

I'm certainly not an expert tuner by any means either. But I have learned quite a bit since I purchased HPTuners a few years ago.

I've looked and looked for something in the tune that could be doing this but I don't see it. The friend I mentioned that had the similar weird little issue had his car tuned by two different professional tuners and his issue still existed until he modified his cooling system.

With HPT I don't think there even is a PID/sensor to log oil temp. Most tables that are related to temperature are ECT or IAT (engine coolant temp, inlet air temp)

Keep in mind, like I mentioned in the post, fuel trims and AFR look pretty darn good. Ignition timing advance is right where it's supposed to be at all times.

Not just at HWY speeds but also any speed, once the oil temp hits 200*+ that's when the "rougher running" starts. You all are probably thinking well what water temp does this issue start at? I don't know since I always have my oil temp up on the DIC. I need to watch the ECT next time I go out. I thinking 182-184 is where the ECT is at when this starts but I'll check.

If I had to bet, it's not in the tune but a mechanical problem. But I'm not sure so that's why I asking for help from all you guys with tons of experience.

 

This is just a thought, and I'm not an expert by any means.
What viscosity of oil are you running and how many miles do you have on your rings? My line of thinking here is that, as your oil gets above 200 degrees, its viscosity gets light enough that it's able to get past your rings and into your combustion chamber. I'm not sure how much oil it would take to cause your engine to run rough, but it might be a small enough amount that it wouldn't show up as smoke in your exhaust.

 

1st 200* oil temp is not HOT--- I don't believe there are any tables that are "oil temp based" that would affect engine performance--other than shutting it down if it gets too hot--probabaly factory set at 300*
I would suspect that it is howver temp based but most likely coolant or IAT temp based---
A changing exhaust note sounds to me like timing is being subtracted via the coolant and IAT temp deducts---retarded timing would make the note deeper and motor boat sounding--
With you daa logger hooked up see what the actual IAT /coolanttemp is The IAT is usually the culprit as it becomes heat soaked and ends up reading underhood temps rather than imcoming air--It's not uncommon to see IAT temps in the 125* range even on a 70* day
THEN go to your tune and see what the timing deducts for the IAT are for the shown temp----Typically the ECM can remove as much as 7-10* of timing when the IAT is above 125*---These engines don't run a lot of timing anyway--At cruise you may have 30* and if the IAT is removing 10* thats a 1/3 !!! and is huge----

 

My car has only about 25,000 well treated miles on it. It doesn't use any oil between annual oil changes. No, I don't have an oil catch can either to check if anything is getting by.
Last year I went back to the same ol Mobil 1 5W-30 since Royal Purple raised it's prices to 9.00 a quart.

Interesting thought about high temp oil ingestion though...now that you bring that up...
I removed my intake manifold in May because I completely removed the Secondary Air Injection System. (purchased new headers w/o the hook-ups) The intake had to come off to get at the one bolt on the back of the drivers side head that held the balance of it AIR plumbing on there.
In the intake runners of the head, to my suprise, was this clear orange goopy ick that had the appearance of oil but was thicker and stickier.

What the heck was that?

 

Yes, I agree with all your saying...
Like I mentioned though...timing remains right where it's supposed to be right thru the point where the car starts it's "not smooth" running thing. IAT is always pretty much the same as the outside temp display on the radio since I have a Callaway Honker. I'm familiar with the IAT vs ECT timing tables.
All those tables were the first thing that I went to look at and monitor.
Going down the freeway Saturday when the motorboating started doing it's thing again I stayed consistantly at 38*-39* of advance, right where it was supposed to be.

O2's are reading perfectly, trims are in line.
THIS IS WHY I'M SO STUMPED.

 

Ok, I'm am going to make a commitment here...
To the person who helps me solve this dumb problem, I will personally mail them a Thank You Card with a check in it.
The amount of the check will be enough to buy a 12PAK OF DECENT BEER!!! My Promise!

 

Ok, here's another idea to throw out there - may be too far fetched, but it's brainstorming.

You mentioned something about cams. I'm guessing that they're non-stock, so you would've had to install them and adjust the valve train(?). Is it possible that heat expansion (in the temperature range that you're seeing the problem) is messing up your valve clearance (specifically) or some other tolerances in your valve train? If I'm not mistaken, the valve train in a pushrod engine will tighten up with heat. Could it be over-tightening as you exceed the 200* mark?

 

I think you are confusing yourself with the oil temps.I would think more along the lines of the conditions that also make the oil temps rise in the summer heat and look at those driveabilty causes.

 

I love ideas being thrown out there!
Hmmmm... Ok... a common denominator between the two cars...
The same shop, which has since changed hands, coincidentally had installed both cars cams along with heads. With their questionable reputation (I have since learned) I doubt they used a pushrod length checker when choosing pushrods. Not to mention shims under the rocker stands for a proper wipe pattern...yeah right! But we are both using Harland sharp modified OEM GM rockers so the wipe is more of a swipe anyway. Could a valve(s) hang open due to heat expansion with hyd. lifters? I'm running 7.4" Comp push rods w/ .020 milled steel valved 243's (at least I ordered them milled!)and a mild comp cam (specs in signature).
With the reduced base circle from the cam grind and the .020 cut heads (hopefully they were cut) (using the stock GM mls gasket, at least thats what I ordered) could the stock pushrod length of 7.4 be to long??? Only one way to really find out...
But I can't believe heat/expansion could make that big of a difference in the hyd. valve train??? But, on the other hand, more heat sure does make a difference in relation to piston slap!
A good thought! I might have to buy a length checker. Thank You.
Anyone comment?

 

You're welcome. I'll think about it some more tonight.

 

I am not sure that heat temp would cause any measurable degree of expansion or at least to cause the problem your having. As previously mentioned, the oil temp is not bad at all. My LS6 runs about 10% higher this time year (gotta hate this metro phx heat which is why it is typically garaged this time of yr).
Again just brainstorming...but just before my coolant sensor went bad i was experiencing similar symptons (not exact but similar). By the way, if you don't mind in would interested in knowing the tuner/shop you reference (via pm). I am installing my own haed/com as soon heads (afr's 215 get in) so i only get po at myself which is oftenbut still am interested.thx

 

Since temperature seems to be a factor you might want to take a look at this table.

Charge Temperature Blending (B4901)
This table compensates for the additional heat added to the air charge after the IAT sensor. This heat source would include air duct, throttle body, intake, and heads. The temperature of the air path material affects the amount of transferred heat. Any non stock additions that effect their temperatures will invalidate the tables parameters. Generally this would include anything that changes engine bay temperatures. Headers, engine bay air flow, insulation, ect.

See also Charge Temperature Filter (B4902)
It controls the rate that (B4901) will be applied.

To temporarily disable (B4901) use (B0109) which by the way should slightly richen the fuel charge since the IAT will control the charge temperature.

Just a thought.

 

Hmmn, could it be something as simple as your A/C? When the compressor kicks in and out, you will feel a slight vibration AND it will kick on your fans. If the compressor is a little worn, it will be noisier and rougher, perhaps also causing the exhaust to seem louder.

Just a thought since you mentioned only in warm weather... Good luck!

 

I would guess a temperature increase to consider would also be higher compression and perhaps less heat drawn away from the cylinder heads due to ceramic coated headers instead of the stock heavy uncoated iron manifolds?
Larry, thank you for the info. Where did you find that anyway? Oh forget I asked...I know, you were born with that knowledge!

Wideband and fuel trims show that I'm already running slightly on the rich side. Wouldn't hurt to take a look, play and see what happens....

 

Love your Avatar! My wife and I were doing just that on vacation last week. I already want another vacation!

The condition exists with the AC off or AC on. Turning the AC on just gets my oil temperature to the 200* mark quicker.

 

Many good ideas out there--- Do you have a wideband ?? If so if you can see if the AFR changes when it starts "motorboating ? May help narrow it down and eliminate fuel as a problem
Also---Do you think you are lifting slightly off the gas when it wants to motorboat ?--- With many cams i have to delete the DFCO system cause with some cams the MAP signal changes and DFCO can inadvetantly enable itself as DFCO is MAP based---you can try that---
ALSO---- If HP has "real time tuning" like EFILIVE i think they call it something else---Try enabling that---That will put the ECM into "open loop" set the AFR at 14.68 and cruise down the freeway--Be careful not to romp on it as PE won't be enabled and you could hurt the motor--but just cruise in open loop and see if you get the motorboating--
If you still do then it is NOT a closed loop or 02 problem--and NO deducts in fuel trims or timing can happen while in open loop in RTT
DO your RPM's change when it motoboats ??? If you have an A4--it could be your converter TRYING to lock/unlock---
If it happens when the A/C or 2nd fan kicks on- you may have to adjust the A/C or fan airflow table adders--let us know---