I really need help. My car will not idle. If it doesn't stall right away, then it 'hunts' from ~ 500 to 1500 RPM then stalls. Even if I try to hold it at 2000 it will still move up and down.

Here's the history:
05Oct07: engine starts coughing and belching smoke. Struggle home. Very long story and 1 month later, find the rear rotor is gone. {it took a long time because the compression test was good??) During this process we traced virtually every wire from PCM to the sensors, injectors, ignition, fuel pump etc etc.

01Nov07: install used engine (66k km) and return the car to stock (it had the greddy turbo kit) The car throws P0172 code. We start looking - checking per manual and replacing parts with new, or from the old engine, and then clearing any codes and re-testing; repeat many times. Along the way we have replaced everything from the airbox to the injectors on the intake system, including MAF & throttle body, front O2 sensors, temp sensor. Checked Air Pump function & relays. Replaced Cat (slightly used) Eventually there are no CEL's or pending codes - but no improvement.

03Dec07 Finally we take it to a dealer figuring their diagnostic machine will detect what we can't. (the first dealer we went to didn't want to look at it) They found a P172 and replaced the rear O2 sensor: no improvement.

07Dec07 The service manager is sure they can find it. They're probably just going to repeat all the work we've done - at $90/hr.

Any ideas - very frustrated and broke - car has been in the shop or running like crap for 2 months :crying:

 

Did you replace the coils?

 

Maybe - we switched new ones in and out at one point - but I'll have to check my notes whether it was on the original engine or the replacement. The car runs fine other than the idle problem. In any case, I still have the new coils and wires in the shop. I'll get the dealer to install on Mon.

Thanks, for the suggestion.

 

Yor problem sounds just like that of Charles Hill as shown in this long thread:
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/rebuilding-my-renesis-115104/

He rebuilt his engine and it would not idle well at all. It also had that O2 sensor code and would stall. He labored long and hard so that you might have this easy answer (I suspect).

It seems like you have improperly positioned injector connectors, causing your management system to struggle compensating for incorrect sizing.

I hope I'm right. If I am you can thank Scott of Mazsport, Mazda Maniac and Charles Hill for the diagnosis.

Paul.

 

Yes, that thread was a great read.

 

What are the LT and ST fuel trims....if have connected the injectors wrong...it should show up in the trims

Also...if the ECT sensor isn't working it could cause it to run excessively rich cause it thinks it's cold all the time..

Does it run in closed loop OK? If so the O2 sensor feedback should be OK?

 

Wow - that's eerie - we have gone through the exact same story, including the MAF bit - sure we had found the problem and disappointed when it didn't help.

We had discussed the injector connections at one point. When I took them off the original engine - I labelled them because it look like it would be very easy to get wrong. But one of the 'real' mechanics installed the wiring on the new engine and assured me they were on correctly. This guy is really good, so...

Since it's clear the dealer won't find the problem, I'll pick up the car tomorrow, take off the upper manifold one more time (I'm not quite as fast as Charles) and check the connections. Hopefully I'll be able to post a positive result tomorrow. I really hope this works.

Thank you,
-Jo

PS: I didn't find that thread in 2 -3 earlier searches.

 

Just got the car from the dealer and it seems much better - only stalled once. But got a P0130 CEL (as opposed to the P0172 the dealer had last week) as I sat in the car for a few extra minutes to see if it would stall. I had it idling for 1/2 hour. It only stumbles when the fan relay trips but doesn't stall. So, I'm not sure what the dealer was saying when he said there was no improvement on Friday?

I'll drive it around and se if it's OK.

PS I noticed my code scanners (I have an Auto Tap and a Harrison Reseach unit) are not picking up RPM or AFR - LTFT, STFT read -178 and -100 but don't move. I can see the codes and few other values.. No idea what that's about.

I'll provide an update tomorrow.

 

What did the dealer do, or claim to do for that matter.

Paul.

 

I guess it's not possible to go to the dealer without a story to tell:
I had supplied the rear O2 sensor which he told me is what was indicated (his price $500, my cost $240). He didn't like that. Then he phones me a few hours later and says the wire is too short, does he want me to splice it. I say sure - whatever. Like I mentioned, the car is working better, but issiung a P130 CEL. So I went under the car to see what they did. The tech installed the new O2 sensor in the front position. I guess the technician didn't move his head 30deg to see the O2 sensor with the short wire in the CAT or notice that the new one has several holes vs the 3 or 4 holes in the front one he took out.

I put the new one in the cat and installed a used one in the front. This made the car go back to the poor idle/stall mode. But did not cause any CEL, on the way home.

So the good news is that it looks like I now know what the solution is; the bad news is I probably already spent an extra $90 at the dealer to splice the wires and I have to spend another ~ $175 (from internet - local NAPA price $330!! list; $245 my cost) to get the right sensor.

It'll take a few days before the O2 sensor comes in. I'll update thread then.

 

I bought the rear o2 sensor on ebay for $100 including shipping from mazsport. I guess I got a good deal

 

The front one is much more expensive from the pricing I have seen.

 

Good & bad news:

I finally got the front O2 sensor on Monday and put it in yesterday. ($126 from Mcculoch site - most suppliers wouldn't ship to Canada??) Most of the suppliers list the front and rear O2 sensors as the same #. So now, I have replaced both O2 sensors. Question: if both are wideband, will the one at the CAT produce the same readings as a narrow band?

Good news: The car will idle on it's own and did not throw a CEL driving home last night. When I let off the gas at a stop light, RPM falls down to ~ 500 and then settles at ~1000.

Bad news: The AFR readings are jumping from one extreme to the other. On throttle, the AFR goes down to 12.5 and stays there, when the pedal is released, AFR jumps up to ~ 18. At idle it will go to 14 but falls slowly too 12.5 again. It's guzzling gas, you can almost see the fuel guage going down as you drive; ~ 1/4 tank for 16 miles [30k]

So I will go back to checking the the injector plugs.

Just BTW, the very first thing we did for this problem was swapping out the front O2 sensor.

 

I thought the O2 sensors were different from front to back..

 

This whole thing smells fishy.

 

Oh - please stop posting in blue text. Its virtually unreadable for those of us using the dark skin.
Just use the default color.

 

NP - I had no idea the blue text was a problem I actually thought it made it easier to read.

 

He set his background to black.

 

??? I didn't set any clours - just typed message - like this one

Getting back to thread: I'm going to post a chronology of all the steps taken to date shortly.

 

Chronology:
[I have included my text doc if this is difficult to read]

Oct 05 -.Driving home, car start starts to sputter/backfire. I got out and opened hood; I could hear SSV flipping open and closed; struggle home. Car stalls in drive and will not start; CEL is P0271
[From this date to today the car has not run properly]
Oct 06 - Check SSV valve and it seems fine. Car starts and I took it for a drive. Everything is back to normal; even pulls boost and power feels strong.
Oct 07 - Go out to clear CEL; car will not start; tow to Mazda specialist next door to my shop.
Oct 09 - 12 car sits because they are too busy to do my work; which they normally do for cost.
Oct 15 – they perform compression check and repot that it is OK; tech starts car and drives it down the street; runs fine until it stalls when he starts back down the street;
Oct 16 - 19 – Based on the successful compression test, I perform the following work with frequent consultation with techs next door: [during this period the car will often start, but is extremely rough and will not stay running] I have the wiring diagrams and all harness check were done using the wiring diagram using procedures per the repair manual and diagnostic document.
• Check for spark with timing light; rear rotor is not firing; check coils per manual, including correction published in this forum. All tests out OK; but I replaced all the coils and wires with genuine Mazda parts; condition remains unchanged; took the new coils and wires out.
• Started tracing wires from components to PCM/ECU connector using wiring diagrams: no faults found and no improvement.
o Coils
o Fuel pump relays; jumped fuel relay; checked fuel pressure – reads above minimum
o Removed upper manifold and traced all wires to injectors [I labeled the injectors connectors so I wouldn’t get them mixed up; removed injectors and tested each for operation.
o Checked the vacuum solenoids at rear of upper manifold; traced to PCM
o Checked SSV visually; operation of vacuum actuator; traced to PCM; later attached wire to allow me to operate valve manually when the engine was running.
o Checked MAF per manual including temperature sensor; traced wires to PCM
Oct 22 – Decide to take it to Ajax Mazda dealer assuming that their diagnostic equipment is more sophisticated that ours. It takes a few days to get an appointment and to arrange a tow; Dealer reports rear apex seal is broken; we tow it back; techs next door confirm the diagnoses.
Oct 29 – Nov 02 - locate used motor with 60km from reliable source.
Nov 5 - 9 we decide to leave the greddy turbo kit off; techs next door install new engine; engine runs fine except for idle problem CEL P0172
Nov 10 - to present, the car will not idle and we start looking for the problem as follows: [some of this work was done by me, some by the tech next door] I have been assuming that all the wire harness tracing done previously is still valid.
• Checked for vacuum leaks – first of several times
• Verified spark from each coil with timing light
• Swapped front O2 sensor from #1 engine
• I swapped upper manifold with #1 engine as this was new two years ago.
• Swapped throttle body and checked operation per manual
• I had modified air filter box and intake hose for the turbo install; so I now replaced the entire assembly with a new Mazda parts assembly; re-installed VFAD.
• Tech found VFAD vacuum line disconnected.
• Removed crank sensor, checked per manual and traced to PCM.
• Checked air pump operation and relays.
• Tech removed and swapped out all injectors.
• Noticed that the idle was steady if MAF was unplugged and notwithstanding that the MAF sensor check out OK we replaced it.
• Dec 07 Once again, I decided the dealer would be able to find problem with their equipment and dropped off car to Ajax Mazda; next day they called and basically said they didn’t want to touch it even when I explained that the turbo was gone and all was returned to stock.
• I drove to Whitby Mazda who, of course confirmed they would find it [this encounter was related in post #10 above.] Get constant P0130 CEL.
• Dec 08 - I started this forum thread.
Jan 03 – Replaced front O2 sensor with new Walker unit; moved the rear one that the dealer installed from the front position to the rear position. Both new sensors look identical to me – the same as the stock rear O2 – the one with many holes in the sender as opposed to the stock front one with holes only at the end. Results are reported in post # 13 above, but basically the car will idle on its own, but engine is running full rich per my CanSan scanner from Harrison R&D

To day I will record the AFR, short and long term trims vs RPM and speed and post them here.

 

Wait a minute! This is a turbo car? At what point in this diagnosis did you examine and/or remove the aftermarket engine management?

Uh...

OK, so you had one set of problems and then you replaced it with a new set of problems.
Why did they replace the injectors? Injectors almost never go bad.
I still maintain that you have your injector wiring wrong. Pulling the MAF causes the PCM to go into open loop, so the wildly fluctuating A/F caused by the injectors firing out of order is not chased in closed loop.

 

Jeff, Charles

Yes there were 2 issues. I included the problems with the orignal engine to chronicle the all the harness and other testing done at that time. (and to whine about how long the whole process has been going on)

All the turbo stuff was removed before we installed the new engine. The idle issue showed up at that time. I read Charles' thread as noted above. As well, I was assured by the guys next door that the injectors were installed correctly. So I put off checking the injector connectors. At that time, the car was at the dealer who told me that the O2 sensor was the problem. (as you said, Jeff, that was probably not a logical progression since the first thing I had done for the problem was swap out the front O2 sensor)

So last night when I got your coloured coded wiring diagram, thank you (I have all the diagrams, too) I decided to check the injectors - only one of them was wired correctly... I traced the 2 Blue/Black ones back to the PCM, to make sure I had them right. As soon as I started the car I could feel the difference. Unfortunately, I must have pinched an O ring when reinstalling the injectors, or something, since gas was pissing out from somewhere. I had been working the last 1/2 hour or so with a massive migraine so I went home at that point. I'll fix it on Wed and report the final results, then.

As always, your help, and all of those on the forum, is much appreciated.

 

I put silicone lube on the rings before I put them on the injectors. This will evaporate almost immediately.
Then, I put the connectors on the injectors and then put them into the fuel rails first.
Then I slip them into their bores, slowly going from injector to injector to be sure the lower "cushion" is seated.
Then I lightly bolt the rail to the UIM and work my way around the injectors again, pushing down on the rails and gradually tightening the bolts.
The injectors should swing fairly freely once the rail is tightened.

 

The reason I "rail" them first is to ensure that the upper "O" rings don't roll as the rail is seated.
I've done it both ways and each has the potential for a leak.
The way I do it is more likely to produce an air leak while the way Ray does it is more likely to produce a fuel leak.
But, both ways can produce no leaks.
Its just a matter of being meticulous.

 

LOL. That took me more than one try before.
Actually, I think this last swap was the first time I did that right.
Nothing quite like a wasted hour of undoing what you just did.