P0171 p0174 p0430
Thread Starter
|
Senior Member
Joined: Mar 2019
Posts: 111
Likes: 7
From: Ohio
P0171 p0174 p0430
Check engine light would come on for a day and then go off. The codes would read po171 and po174. Both lean codes we are going to smoke test in a couple days to see if we can find an intake leak. Today a PO430 (cat below efficiency) was showing for the first time. I'm just wondering if the car running lean would cause this code to come on? also it is a 2009 XF with a 4.2. are there any common known air leak points on these engines? Also what side is the p0430 referring to when it says bank 2?
Last edited by garysaunders85; Jan 3, 2020 at 11:12 PM.
Senior Member
Joined: Jan 2020
Posts: 261
Likes: 61
I had this happen on my 4.2 SC, the smoke test found nothing, turned out to need a new coil pack.
However this didn't entirely fix my problem. it also had a faulty MAF sensor - but it hadn't totally failed it gave readings that were in range of the allowed output but not actually related to the amount of air coming in, if you read the output via the OBDII it seemed plausible. It took me about 3 months to diagnose this because it is more likely to be a vacuum leak and I distracted trying to find it, by which time both cats had been destroyed.
The two things that led me to the MAF were:
However this didn't entirely fix my problem. it also had a faulty MAF sensor - but it hadn't totally failed it gave readings that were in range of the allowed output but not actually related to the amount of air coming in, if you read the output via the OBDII it seemed plausible. It took me about 3 months to diagnose this because it is more likely to be a vacuum leak and I distracted trying to find it, by which time both cats had been destroyed.
The two things that led me to the MAF were:
1) that the engine would feel lumpy on a cold start (overnight at less than 10C) or hard acceleration at high RPM. It was most noticeable when the engine was running in open-loop mode, i.e. it was ignoring the data from the O2 sensors and relying on the MAF & MAP etc to get the fuel mix right. When the O2 sensors kicked in and it went closed loop (about 1-2mins from a cold start) the ECU got better at guessing the fuel mix based on the output of the engine rather than the input. Which led me to do the test in point 2 below.
2) using a can of MAF sensor cleaner. If you've never used on of these its basically an aerosol degreaser that is designed to dislodge muck and quickly evaporate leaving no residue. You run the engine at about 2000 rpm, fire it into the air intake after the air filter in short bursts, it should quickly coat the MAF sensor with fluid, which will cause it to send random readings to the ECU who in turn will almost stall the engine trying to compensate. Once the cleaner has evaporated (a few seconds later) the MAF should start sending sensible readings and the engine will pick up again to 2000rpm. I found that when I did this on bank 2 the engine behaved as predicted, nearly stalling, however when I did it on bank 1 it made little difference to the output of the MAF and therefore the engine speed. Quick replacement of the MAFs and it was all back to normal, well normalish, because by now the cats were screwed.....
That meant two new cats, which are not cheap, but on the plus side aftermarket high performance (and nicer sounding) cats are half the price of the genuine Jag ones.
2) using a can of MAF sensor cleaner. If you've never used on of these its basically an aerosol degreaser that is designed to dislodge muck and quickly evaporate leaving no residue. You run the engine at about 2000 rpm, fire it into the air intake after the air filter in short bursts, it should quickly coat the MAF sensor with fluid, which will cause it to send random readings to the ECU who in turn will almost stall the engine trying to compensate. Once the cleaner has evaporated (a few seconds later) the MAF should start sending sensible readings and the engine will pick up again to 2000rpm. I found that when I did this on bank 2 the engine behaved as predicted, nearly stalling, however when I did it on bank 1 it made little difference to the output of the MAF and therefore the engine speed. Quick replacement of the MAFs and it was all back to normal, well normalish, because by now the cats were screwed.....
Thread
Thread Starter
Forum
Replies
Last Post
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)