Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Hi Boys, Got a 2001 astra in. Customer has fitted new coil pack, plugs and upstream o2 sensor. Has bad missfire , compression test ok, looking at data ignition advance is jumping every where from 19 - 1.5 on idle.
o2 before cat is 20mv,, o2 after cat 79mv. when hot
There should be a bias voltage on the o2 sensors,koeo usually 454mv,use the finger on battery post to end of t pin back probed on the signal wire to check wiring integrity,on both sensors.
Hi, yes tried this, both sensors reacting form + and - terminals. on idle when hot upstream is on 20mv downstream is 98mv. misfiring, add propane both o2 jump up to 900mv engine runs smooth, remove propane and they go straight back down to where they were. looked for vac leaks, fuel pressure sticking at 55psi idle and WOT.
thinking clogged injectors ?
Hi, when driving feels smoother, both o2 dont move even at WOT, when you back off the upstream goes from 20mv down to 0mv for couple of seconds then back to 20mv.
ive tried unpluging maf and does nothing. it has a 12v, ground , iat, and signal with 5v when unplugged.
when its cold it idles very rough with popping from exhaust, untill o2 heaters kick in then sort of calms down. compression is all good.
Any after market induction pipes?Non standard Aiir filter?i have seen this fault when non standard items are fitted,what about a throttle body clean and relearn,reset adaptions,
the MAF readings look o.k. so far and do not point to a vacuum leak( if you divide the kg/h you'll read g /sec which is more common). The according fuel trims are of interest in order to know if the ecm is trying to control the fuel delivery. I'd expect them to be maxed out, positive.
The data and information you provided so far suggest a fuel delivery issue, esp. if the trims really are maxed out. Is there a chance that the inyectors were changed/are different? Try to measure not only the fuel pressure but also the fuel volume.Do the plugs indicate lean burn, all of them?
One thing that does not quite fit is that fuel delivery problems are more notorious under loaad/higher rpm.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Hi, its all origional intake, filters etc, throttle body clean, it idles very rough for about a minuet when cold then settles down slightly when starts to warm up , but add propane and idles smooth. its fuel or air ????
hi, thank you for getting back, injectors are all origional from new , so 19yrs now. plugs are looking new, nothing on them still, been in for a month or so when customer fitted them.
Ive ordered a n injector tester to do a balance test, see if i can see any thing more?
Its doing my brain in, thank you for your help
Hi, when i get delivery of my injector tester, what would be a good pressure drop on injector over a 10sec burst?
Or are these just a guide / balance test comparing to each injector ?
Sorry just looking for guidance on what to look at next.
Do the fuel trims show that the ecm is trying to add fuel? There is a chance that there is no reset for the throttle body on those, just goes by the voltages...
Could you post a complete list of generic OBD2 data with the engine warmed up, please.
The fuel injector drop test is a relative comparison. The pressure should drop equally on each injector, a difference of more than 1 psi shows a problem.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
The O2's read lean. They recognize fuel enrichment by propane. Their wirings are o.k. Fuel pressure is at spec. Code for fuel trim issue. Maf readings look o.k.
You may want to look for an exhaust leak that is fooling the (upstream?) O2 sensor.
As the misfires will make the O2's read low as well: Do they still read lean when the engine is not misfiring?
Do you know why the owner changed the oxygen sensors and do you have the original ones?
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Hi Juergen, thank you for getting back to me, it is much appreciated.
I have just spoke to owner and he says he changed the upstream o2 only,, about 2 months ago and didn't make any difference whatsoever, he didn't have any codes regarding the sensor he just thought he would change it to see if it made a difference.
He doesn't have the old one either.
He also mentioned he has fitted a new Maf sensor last month too.
I have noticed that this morning when I had another quick look at it the down stream it was on 15.6 and wouldn't move with propane ??
He has suggested replacing both O2 sensors and see if does anything.
What do you think?
Do you have an ignition scope and/or a gas analyzer. Do repeat the O2 ssensor checks once morre, from bias voltage over circuit integrity to responsetivity, both sensors. Make sure they are not mixed up, front one connected to the back one`s harness and vice versa.
At this point I see no proof yet sugessting to change both sensors.Report your findings on the O2 sensors.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
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