Hotter than a snakes a$$ in a wagon rut.

[goodburbon]

I went to the exhaust shop yesterday to have them patch a hole and re-attach a hanger. While I was there the tech pointed out that my exhaust was getting waaaaay too hot, and noted that the pipe was blued from the engine to the muffler.

The engine temps have been high lately, I can't run the AC in traffic or the engine will overheat. I did some searching and was beginning to think that I had a leaky intake manifold gasket and was running lean. But my rear axle is covered in soot, and my exhaust is extra hot, which I think indicates a rich condition.

Relevant information.

97', 4.0, cone air filter, constant bore stock TB, TB spacer, Banks header, oxy sensor<1year old, 3 inch exhaust from the header back. New 3" magnaflow cat installed with 3" exhaust. 13-15 MPG on 33's with 4.10's (rich?). 180* thermostat, Jet stage 2 Chip, using 93 octane (jet chip requires 91). last codes thrown were for incorrect purge system flow, but none in the last 6 weeks. It has been running around 200-220* since ambient temps have been over 90*F.

Any thoughts as to cause and solution?

 

[andrew2516]

Maybe the 180* thermostat is making the engine dump more fuel than it should

 

[goodburbon]

That thought had occured, but the engine is running 200, not 180*.

 

[87manche]

intake temp sensor.
Stuck open injector
o2 sensor on the way out
coolant temp sensor for the ECU.<-Not sure about that on your 97, but my 87 has one for the guage and one for the ECU.

 

[goodburbon]

forgot to mention: brand new IAT sensor.

Pretty sure its only one sensor for the 97 and up, so that leaves

oxy sensor and/or injector. I had come to this conclusion, but I'm not sure how to tell which it is........you have to try to think like the computer.

ok, how's this for a likely scenario

One injector is stuck open causing a rich condition in one cylinder, as that exhaust is pulled into the header it ignites, heating up the pipe and buring up any excess oxygen causing the oxy sensor to read rich, and leaning out the other 5 injectors causing a perpetual imbalance and overheating....and soot deposited all over my rear axle.

Possible? Likely?

 

[JTwthaXJ]

I had an injector on my '97 about a year ago, it ran a little rich but the temp never went that high. I was running a 180* t-stat at the time. Check e-bay for 19lb injectors (five-o motorsports was where I got mine from), with the temp thing, when was the last time that you flushed the coolant. I also upgraded to a high flow hesco water pump and a 3-core GDI radiator, temp never gets above 200* unless sitting in traffic with the a/c on full blast. Never finished the exhaust so the Jet Stage II is still in the room at the house...

 

[87manche]

I might suggest that you get yourself an infra red temp gun, and then put it on each cylinder exhaust it might help to isolate which injector you need to look at if you suspect a malfunctioning injector.

 

[old_man]

High exhaust temps are normally caused by running too lean, not too rich. Adding headers will tend to make an engine run more lean. Get a tailpipe sniff to see what your engine is doing. If your NO readings are way high you are running too lean. You may need to get a map adjuster.

 

[goodburbon]

My last multimeter had an IR temp sensor on it, but then somehow it lost calibration and someone needed it more than I did apparently. Thanks Old man, I really respect your input, unfortunately we don't have the capacity to do that here.

I have have to work with what I know. Loads of soot which indicate a rich condition and an overheating exhaust system which indicates a lean condition. Is it possible that I have a lean condition at Idle and a rich condition at 2300 rpm? That would explain overheating in traffic and could be explained by a bad TPS, but I would expect that to have the opposite effect. A simple lack of airflow would also explain this. I intended to get a better radiator until I discovered the excessive exhaust temps. When I first installed the exaust system I noticed that the catalytic converter was blue by the time I got home. I thought this was normal at the time. Is it possible that the 3" magnaflow "high flow" catalytic converter is more restrictive than the stock unit? The overall body case size of the converter was smaller, which I did not particularly like, but assumed that the passages were designed differently to make it "high flow".

 

[Wa Woody]

What do your sparkplugs look like? Are they all the same color, or different? White deposits on plugs also indicate a lean (hot) condition. Old Man is correct that the header will cause the exhaust sys to run hotter (leaner burn). Therefore, if your new cat restricted the exhaust flow it would cause the exhaust sys to run cooler (richer burn). A NOx reading and temp readings with a IR gun would help a bunch. It's very possible that your fuel sys is fine or even rich, which would explain the soot, while your cooling sys isn't up to the task of cooling the motor sufficiently. Good Luck

Woody

 

[outlander]

Maybe the 180* thermostat is making the engine dump more fuel than it should

That was my first thought.Stock is a 195*

If you suspect a stuck open injector I'd advise to get that fixed asap because it will wash down the cylinder of oil and fubar that cylinder fast!!!

 

[BlueCuda]

You can be to rish and cause the temps to go up. What happens is the extra fuel burns in the pipe giving a false reading on EGT if you have a guage. If your rear axle is covered in soot this could be the problem.

 

[goodburbon]

I haven't had time to really fool with it, but I did go to the U-pull it and happened to grab some injectors from a v-8 town car while I was there. I pulled out the stock injectors when I got home and there was all kinds of red crap in the line. I ended up pulling them all and bumping the fuel pump a few times to flush it all out. It had to have been running lean with all of that trash in the injectors. One question remains though, why is there so much soot in the exhaust?

 

[goodburbon]

Had a good test run today in traffic. It's definately running better at speed, and not as much heat from the floorboard. I was actually able to keep the AC on the whole way home without it overheating, but it got up to the 225 mark after 20 minutes in traffic, it would have overheated had I not gotten on the interstate very soon. I put in the Lebaron hood vents a few minutes ago and we'll see what kind of difference that makes. I think I still may add a 10" electric fan between the grille and Condenser. Depending on how it does tomorrow.