I have had a sluggish acceleration problem.
A couple of weeks ago, I fitted a new front O2 sensor.
This afternoon, I fitted a replacement MAF.
On testing the car, I got a P0172 warning, Fuel Injection Too Rich.
Acceleration lag seemed to be cured.
No evidence of backfires, so I am guessing that the ignition is O.K. (New plugs fitted anyway).
Any suggestions for the next thing I should be looking at ?
Phil.
What was the reason for fitting these parts?Any diagnostic testing performed?Are these parts original Mazda or cheapo after market?A front lambda sensor is cheaper from Mazda dealer than non genuine.
I bought an OBDII reader, last year, because the engine warning light came on. The only fault code was for the front O2 sensor.
However, the car was left garaged from November till the end of April this year.
When I got back to the car, I replaced the O2 sensor with a new one from MX5parts, (IL Motorsport). I cleared the fault code, and there have been no issues since.
Then I started having acceleration lag problems, and the warning light come on again, this time for the MAF, which I replaced with a second hand one bought on here.
On test, this appears to have eliminated most of the acceleration issues, but, after the test, I had a new warning light, this time for P0172.
I have taken a quick look at the live data, with the engine running, but I have to admit to my ignorance as to how to interpret the values I am reading.
However, I suspect that I am getting an indication that the variations on STFT, LTFT and SHRTFT are too wide, but here is where lack of knowledge kicks in.
I don’t know what values I should have, and I don’t know what to do if the values are not as they should be.
My major problem is that I am in Spain, with the nearest Mazda specialist about 100 km from my place.
(Added to the fact that some of the Mazda dealers appear to be rip-off specialists. One quoted me 650 euro for a MAF).
Phil.
I think Phil has done the right things as P0172 generally indicates a problem with the precat lambda or MAF. Possible, with the right equipment which most of us do not have, to test the lambda but not the MAF as far as I know. My advice given this sort of problem is to replace easily accessible parts with known working ones to quickly discount that part as the problem or hopefully cure it.
aside from the unlikely like a wiring fault, vacuum leak or exhaust leak, the only other part I would try is a throttle body. Probably only the TPS that could possibly cause this but replacing the whole unit could be worth trying.
How much is a MK2.5 precat lambda sensor from the dealer missfire? Last time I enquired I think the figure was £180 or about four times the price of an aftermarket sensor. MX5Parts now have the genuine item listed at £120 which is usually a significant mark down from the dealer price. When I look at the items on MX5Parts website both the Mazda original and IL Motorsports aftermarket sensors appear to have a Denso manufactured sensor plug. On that basis and the fact that this is a regularly supplied direct fit item, i would expect it to work with no issue.
Back to working on my car, as I had to spend some time cleaning up the garden, and a lot of time watching cricket.
I am trying to solve an acceleration lag problem.
What I would like to avoid is a trial and error process, in which I end up spending money replacing components, only to find that the problem is still present, and was not caused by the components I already replaced.
The next step seems to be checking out and cleaning the throttle body.
Apparently, according to the Haynes manual, there is no adjustment possible for a MK 2.5, TPS, but is there any way of checking if mine is still in good condition ? How likely is it that the TPS has failed ?
£145 to replace a component which might not be faulty is potentially, a lot of money for nothing.
Also, according to Haynes, there is a gasket between the throttle body and the intake manifold, but MX5parts says no. Can anyone confirm this point ?
Following the throttle body, I was thinking of removing the air intake chamber, and checking and cleaning the injectors.
Again, Haynes says to replace the intake chamber gasket, but MX5parts does not have these in stock, and they are available on special order only. My question then is this. If the intake chamber / surge tank gasket is not a stock item, how likely is it that I will have to replace this ?
How important is it to replace the O rings and seals on the injectors, and what does the injector cleaning process involve ?
Any help and advice will be welcome.
Phil.
Today, I removed and cleaned the throttle body.
The only real problem I encountered was that I tried to remove the idle screw, and discovered that it was not possible to actually remove the screw from the throttle body, so I was unable to clean behind the screw.
Then I realised that I did not know how far to screw back in.
Is there a method of setting this correctly, or is it simply a matter of adjusting until the revs hold at 800 - 900 rpm ?
Yesterday, I bought myself a digital Multimeter, and following on from a couple of videos I found on You Tube, it appears that the TPS is functioning. I had a high resistance when the throttle was closed, at 3.4 or 4.8, depending on the multimeter ohm setting, (I failed electricity, so feel free to take the Mickey). However, as I opened the throttle, the readings declined, as I would have expected, and dropped to 1.2 fully open, (compared to the 3.4 when closed). There is no spec for this in the Haynes Manual, so can anybody tell me if this range of values is correct ?
I also checked the idle air control valve resistance and got a reading of 11.2, so this appears to be in the rage of 10.7 to 12.3 ohms, specified in Haynes.
One surprise was that there was a metal gasket (or spacer), between the throttle body and the intake chamber, whereas MX5parts had told me that there is no gasket.
It seemed in good condition, so I cleaned it up and re-used it, but I also added some liquid joint on both sides of the gasket.
With fault codes cleared, I took the car for a test run on a winding uphill road, so I was using the gears and the revs constantly, and I noted a definite improvement in acceleration, especially in the 2,000 - 3,000 rpm range, but still not perfect.
When I got back to my place, as I was fiddling with the idle screw, I noticed that the check engine light was on again, and found that I had P0172 again.
Could this be due to the idle screw setting ? If so, back to my question at the top of this post.
Any suggestions for the next step in my fault finding journey would be more than welcome.
Phil.
It looks as if I may have solved my problem.
Talking to my son, over the weekend, he asked if I had tried one of the snake oil solutions.
He mentioned the hydrogen cleaning and TerraClean processes, and said that he had been a firm non-believer, but that he had so many of his customers tell him how good they were, that the evidence seemed to point in the right direction.
Anyway, I found a reasonably local company that does the hydrogen process, so on Monday afternoon I took the car in.
After an hour on the machine, the difference was amazing, but the acceleration lag was not cured 100%. The guy who runs the garage took my car out for a quick spin, and came back and said to me “fuel filter”, something that I had hardly considered.
This afternoon, I fitted a new filter, and when the petrol had evaporated from my hair, face arms and upper body, I took the car for a test, and I feel like saying “bingo”.
However, my recent experiences have taught me to be cautious about crying victory too soon.
Surely a partly blocked fuel filter wouldn’t result in a rich mixture, but the opposite, i.e. too weak if it caused a restriction to fuel flow.
Did you disconnect the battery to reset the ECU? Some faults won’t clear until this is done.
I understand your reaction, especially as P0172 points in the opposite direction.
I can only assume, for the moment, that P0172 came up as a consequence of the different sensors sending signals that the ECU had difficulty interpreting.
As I see things, the ECU tends to cascade fault codes, probably based on a scale of most likely to least likely.
Because of the sequence of codes that came up:
I had already replaced my O2 sensor, with no real idea if the original was faulty,
I had already replaced my MAF, with no real idea if the original was faulty,
I had checked all of my hoses and found no obvious signs of leaks,
I had cleaned the throttle body, and tested and confirmed the TPS and IAC for the appropriate resistances.
At this point, the Live Data on my OBDII reader suggested a problem with Short Term Fuel Trim, which appears to have been corrected with the hydrogen cleaning and the new fuel filter.
I would be more than happy to state that I had solved my problem, but I actually solved nothing.
The fact is that the problem appears to have been solved by a “snake oil” solution and a new fuel filter.
Phil.
p.s.
Yes, I did disconnect the battery.