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[haslamg]

Guys

I got this motor last year with 83K on it.  In the space of a year, it's been running rougher and rougher at idle, despite me swapping out more and more items.  It only returns about 16mpg despite babying it on motorways and A-roads.  It has a multipoint LPG system fitted, the symtoms below happen either on petrol or LPG.

At the RPM needle it appears to idle quite smoothy, but at the exhaust, it sounds like it's blowing, chugging and missing, despite having a nice new back box.  If I hold my hand under the exhaust, it is randomly pushed away by quite strong bursts of pressure.

Parts / procedures done so far:-

1) New cap, rotor, leads, coil and plugs
2) New TPS and IAC
3) New back box
4) Replaced cracked exhaust manifold
5) Cleaned throttle body assembly
6) Checked for vacuum leaks

I'd suspect the fuel injection system if it didn't happen on both petrol and LPG.  The ZJ pulls strong, seems to run ok at normal road speeds and isn't loosing a drop of coolant or oil.

Here's what the exhaust sounds like at the tail pipe (90Kb):-

http://https://mobile.tatmuss.com/zj002.wav

Any thoughtettes?  I really don't want to take it to Chrysler if I can help it.

Big thanks.

G.

[JamesH]

O2 sensor?

[Mike Pavelin]

Do a compression check.

[haslamg]

OK.  I'll get a kit and post the results.

Thanks.

G.

[haslamg]

Jesus wept....took a while to get a compression gauge that would fit.

Here's how it looked:-

Cyl 1 - 149
Cyl 2 - 150
Cyl 3 - 150
Cyl 4 - 150
Cyl 5 - 150
Cyl 6 - 168

The compression built nice and quickly - no dramas.

I've also swapped out the o2 sensors.  Once the engine has warmed, the noise reduces, the rich running smell dissipates but it still sounds a bit 'chuggy'.   There is a slight shake to the engine too, until it's warmed.

It pulls like a train on the motorway and spends its life in the outside lane, pushing BMWs out of the way.  It really does run fine but it cannot be running efficiently when idling like that.

Any further insight into what might make this car chug-chug-chug at idle be it on LPG or petrol?

Thanks guys.

GH

[haslamg]

now then, now then....

Is this going to sink into oblivion without any answers?  

You're my last hope fellas, to avoid me paying a £110 p/h labour rate down the dealers.

Thanks.

GH

[Panic mechanic!]

where do you live it may be easier to bring it round to a birty that can help you diagnose, whats going on

[wazza]

the idle sounds too fast and as if its missing a pot or two (oddly)

im not sure but ive just spent the last 10mins listening to that over an over!!!

mine runs like a bag of shite on petrol but is almost sweet as a nut on gas
(single point) i bought mine with a nakkered engine that was underfueling an when hot an ideling badly an no power sounded nothing like yours!!!!

ive still got to play with mine to find out why an adjust the timing to suit the gas. the only reason i hav'nt done it so far is, it runs fine standard an i can't be arsed!!!

ill try an get it all done this weekend an let you know what i find an see if i can get mine to replicate yours!

[Bubba]

i rekon its the tps

[greggmo]

yup.

[haslamg]

Wazza - thank you .....very much appreciated  :-D

Thanks.
GH

[Bishops Finger]

THo not a Birty a call to Chris at Surry off Road may be a good idea