Blitzkrieg3002

so my 1991 toyota pickup's been making me scratch my head... a while back my CEL came on and i checked the codes, pulled a 43 & 71, i dont remember what i did it was over a year ago. i got it to turn off, and it's never came back on ever since. well recently its been getting horrible gas mileage. around 13 - 15 mpg, and i've been getting some overheating issues. i replaced the radiator last week and changed the oil, and i havn't had any overheating issues since although it seems to run hot. my CEL hasn't come on, but last night i thought i'd check the timing, so i jumped the diagnostics lead, hooked up the timing light, and found out i was sitting at 10 BTDC. i then proceeded to tuned it properly to 5 BTDC. then figured i'd pull the codes since i had the lead jumped already (even though my CEL hasn't been on) and it pulled 43 & 71.

even though it seems my overheating problem is fixed, the truck still seems like its running hotter than it should. it's idling fine, and passed CA emissions tests 6 months ago after installing a new CAT. one thing i find odd is that when it was overheating/boiling over, i'd hear the steam start to whistle out the radiator. when i'd look down at the temp gauge on the dash however, it was sitting just a tad above the 1/2 way mark. the truck runs normally just a tad below the 1/2 way mark. never ever have i seen it get up even close to the red. seems odd that it's overheating and the temp gauge is still so low. i'm not quite sure what this means, but i feel as though my MPG is not where it should be. averaging 180 - 220 miles on 16 gallons...

based on my symptoms does anyone know where i should begin to look?

symptoms:
codes 43 & 71 pulled
engine seems to run hotter than it should
13 to 15 MPG


i ordered a vacuum hose assortment and i'm going to replace all those hoses and make sure their routed correctly based on the diagram under the hood for starters.

i also was reviewing thread:
https://www.yotatech.com/forums/f116...74/index2.html

Blitzkrieg3002

found 2 vacuum hoses going from the throttle body to the P and R on the EGR vacuum modulator crossed. I corrected those, and then proceded to test a few of the EGR components. EGR valve is working properly, but the EGR Modulator seems to be bad.

according to my Chiltons FSM, it states that with it off and plugging P and R, you should be able to blow into Q with it freely flowing out the filter. well its extremely resistant, the same way it is when you have it with the engine on at 3,000 RPM as it should be then so i think its bad. is this correct?

HawkStrong16

This may seem odd but how does your oil look?
I was having simalier problems and it turned out to be my headgasket had blown, it was running a little hotter then normal.

Try getting an oil report done at http://www.blackstone-labs.com/
The kit is free and report only costs $20. $30 if you want a TBN.

If nothing else you can see how your oil is doing. haha

Blitzkrieg3002

gosh i sure hope not, i dropped the whole long block in about 15,000 miles ago because of a blown head gasket, i just did an oil change 5 days ago and it looked normal not milky like when i blew my last one, also coolant looks good. i am keeping this in mind tho i've been checking and worried about this.

Blitzkrieg3002

i think i'm going to do that oil test just for the hell of it to re assure myself, or make me sad

Blitzkrieg3002

not meaning to bring a thread back from the dead, but just to post a conclusion, it was the head gasket. I replaced it and running strong