could use some suggestions on what to look for here.

My 22re has 533miles on it and it is running great in every way so far as i can tell except: it is idling at about 1k rpms (a little hi) and when i decelerate it pops, once in a while loud enough to maybe call a backfire. the heavier the load before decel, the more excessive the popping. Running brand new LCE street headers and 2 1/4 exhaust WITH a new hi flow cat.

I just adjusted the valves and re torqued the head, exhaust man, and checked timing-all seems to be good. i am pretty sure all the vacuum hoses are routed correctly. new plugs, wires, cap/rotor, injectors etc....

i was told that the RE shouldn't backfire at all by the tech at LCengineering. I'm a little worried about burning valves or doing something else to mess up this sweet new long block. its in an '85 sr5 pickup. any ideas appreciated. thanks

 

I have the same problem ...

most I have been told is a small leak from the exhaust will caust this problem .. but I think that is BUNK .

I believe this is a "rich" running engine , but I just cant figure it out .. I have replaced EVERYTHING .. except the air flow meter .. and still NO change !

one of my issues as well , is I dont have "fuel tank pressure" (the gas cap dosnt whooshhh when I remove it ) some say this is not important , but I know it is .. does yours do this ????

my throttle body shaft is also "loose" .. I can actually move it , changing the values on the TPS ..

dang .. these things are gettin' old ....


.

 

did you guys lose MPG when you put your 2 1/4 exhaust on. cuz i think iam. but mine runs fine. i am running hi flow cat pace setter header and 40 series flowmaster.

 

my exhaust stayed stock .. but i'm down about 25% on fuel economy ..

 

down like worse mpg?

 

also check your egr valve there is a hose that goes down and hooks up to the vacuum lines(steel) and that can get clogged full of carbon. just put a lil carb cleaner in there let it set and then push a piece of wire down there to clear it out. that valve actually puts exhaust into your intake at high rpms. idk why but it does, it doesn t really make sense but thats the way it worksif you have any more questions email me.

 

yep ..

I use to consistantly get 400KM's per tank of fuel .. now only 300

I know it's "overfueling" (backfire/ popping , and black exhaust tip) I just cant figure it out .


in my case , it was originally a burnt valve .. so engine was rebuilt , thinking this would "cure the problem .. it did not . EVERYTHING was either replaced , or cleaned . except air flow meter , and computer . I'm going to try the computer next I guess .

 

Check the dashpot adjustment/operation. That is located below the throttle linkage on the throttle body and it slows the closing of the throttle plate when you let off the gas suddenly:
http://www.4crawler.com/4x4/CheapTri....shtml#Dashpot

DP is circled in green:


It has a check valve below it that lets air in fast but lets it out slowly. I like to adjust mine so the throttle linkage depresses the DP plunger about 1/2 of it's travel.

 

well, my exhaust is all brand new from headers to tailpipe so i don't think there are any leaks there.
my throttle shaft does have a little play, but i am pretty sure it is okay for there to be a little, could be wrong about that tho. seems like a little extra air flow might raise the idle but cause backfire?

As far as the mpg question, i haven't actually checked mine yet, i was getting about 21 before my issues that brought on the rebuilt LB. seems to be okay,but i'll b checking for sure on this tank.

The egr idea sounds promising, but because my vacuum pipes were so clogged when i was re installing them, i just bypassed them and ran hoses until i can find a new set of pipes (any leads on where to get one of those?) and i cleaned out the valve pretty good i think.

hey slacker, did you actually replace your throttle position sensor? i have a feeling my problem is coming from there even though it seemed to test out ok with the meter. those things are Flippin expensive tho!

I am going to try adjusting the throttle dashpot too, but i don't think that's it because it still pops long after the effect of the dash pot has passed, like if i am coasting in 3rd or 2nd down a grade for a long period, it just keeps doing it.

could be something to the airflow meter too, don't really get how it would, have to read up on that one i guess. never boring. just psyched to be rolling in the yoti again.

 

yep .. I did replace the TPS ..

I checked out 3 of them till I found one with correct values ..

I also replaced the throttle body with one that had "minimal" throttle shaft movement (checked with TPS attached and changing values)


I must admit , I have never even looked at the dash pot on the TB .. I just "assumed" a good TB would have a good dash pot .. I will be sure to check it out ..


Although , I have not replaced my air flow meter .. I have changed the "values" on it as well .. there is a blocked off plug ..Penteonometer(sp) .. where you can adjust .. I drilled , and tried different adjustments over time .. and surprisingly .. absolutly no change ?

I even took my truck to a shop , with a "diagnostic" center .. where they hooked all the sensors up to the machine , to see if all were working .. and ALL checked out "A OK " ..

my truck absolutly purrs like a kitten .. starts on the first crank (every time) , and runs like a champ .. I just am not getting the "best" fuel economy ??

.

 

I read if the valves are adjusted too tight is the only way to burn a valve. Because it doesn't have time to cool against the seat. You asked about burned valves in the top post.

One thing about the TPS is to do a sweep on an analog multimeter and see if any dropouts occur.

 

You might also check your timing chain. Your cam timing could be off due to a stretched chain, etc.

 

I wonder if it may have something to do with the EGR system. Maybe it's malfunctioning. Read as: If it's connected to the exhaust system it may be suspect. Also does the egr connect to only one header tube or to all four?