Engine/Transmission (1994 - 1998) Odd Symptoms--higher EGT & more boost

[rrausch]

I've been having strange symptoms lately with my 1995. EGT's are about 600 degrees on the highway, driving unloaded, instead of the usual 450. And it takes longer to cool down before shut-off. And boost seems up a bit.



Could these be signs of a plugged Cat?



All fluids are at normal levels. I don't see anything out of the ordinary when inspecting the engine compt. Filter minder hasn't moved. Any ideas?

 

[gwagner]

It sounds like its a excessive amount of back pressure and the cat would be my prime suspect. i'd say pull the cat out and "misplace" it . i "misplaced" mine a whilie ago and noticed a little more noise and my egt's dropped a little also.

 

[illflem]

Have you been running the A/C since the temps went up?

The A/C will raise your egts about 100° and with it running it's sometimes impossible to get down to shutdown temp.

If not it's probably the cat plugging up, they usually do at around 80k.

 

[rrausch]

Bill, is there some simple way to test for a plugged up cat?



I do run the AC most of the time when I am out here on the Left Coast, and I did take that into account. But even stranger is that today I drove the same route (I-10 to 405 to 101) and the EGT's were almost normal!! They were a little high, but normal for that route, unloaded is about 450+. 2 days ago EGT's were above 600, while today they were about 490 or so. Strange! Maybe my gauge is haywire.

 

[illflem]

About the only way I know how to check for plugging is to measure the exhaust pressure. You do this from the same location your post turbo pyro is hooked up.

Problem is that you would have to know what the pressure was before the cat plugged to know if it was creeping up. Easier just to pull the cat and install a straight pipe, keep the muffler if you like.

A good hard run can clean the cat out a bit but it's still just a matter of time before it's plugged.

 

[rrausch]

Well, I am making a run to S. W. Missouri around the end of this month. If it doesn't get worse by then, and if I haven't "lost" it by then, maybe that trip will scour it out.



Thanks Illflem!

 

[wcjp]

Hey Illflem,



Couldn't he just unbolt the downpipe at the turbo to see if this makes an appreciable difference?

 

[illflem]

I guess if Robert could handle the noise and soot deposits under his hood it could work! It's sort of the same idea as a straight pipe. Straight pipes were originally called test pipes and said right on them-

TO VERIFY CATALYTIC CONVERTER EFFCIENCY ONLY - NOT FOR PERMANENT INSTALLATION

 

[Andy Redmond]

My bet is that the Isspro (?) gauge unit is malfunctioning. Find a shop with a pyro tester to test the gauge head then the thermocouple and lead wires.



I bet a new thermocouple fixes you up. Part # R658 (if Isspro). $30 +/-





Are your readings pre or post turbo? 600-750 deg. F is very normal for pre-turbo readings.



If 450 is the norm, you must be post turbo?



Good luck

Andy

 

[fortunate1]

I experienced something similar to this last winter, and posted to get some feedback. EGTs were slightly higher on a highway run that I customarily make a couple of times a week. Boost was up a little too. No A/C, no cat. What it turned out to be was I had run up against a pretty stiff headwind on that trip, and the engine had to work a little harder to overcome that extra resistance. Later trips along the same route (without that much wind) brought the EGTs back to where they usually had been.



Just something else to think about. BTW, you really should give that cat to the SPCA, PETA, or Soot-Suckers Anonymous.

 

[rrausch]

Whatever it was, it was all cleared up today! I don't understand it yet, but today I was running 65+ on the freeway, and the EGT's read a steady 450. Maybe it healed itself! Hopefully it won't come back.