Air/Fuel ratio problems

[tbondo]

I am looking for anyone running a similar setup that has had air/fuel issues. I recently swapped a KL-DE into my RS 4 cylinder. Here is a little background on my setup:

2.5 KL-DE 5 speed
Unknown ECU from 93 Probe GTS
KL-02 Mass Air sensor
Probe Addiction headers
High flow Magnaflow cat
2-1/4" cat back exhaust into Magnaflow muffler
3" ebay intake modded to fit

Now to my problem. My car is running a little rough at idle and has a hesitation once warm and under throttle. I was told it seems my air/fuel ratio may be off due to the stock fuel system and the upgraded air/exhaust system. I do not have any CEL lights so that check is out. I know others out there have to have a similar setup so my question is, how have others solved this issue?

Also how many O2 sensors are you running? I currently have 1 in the front and 1 in the rear header. I was told there may need to be one or two post cat?

[Nd4SpdSe]

Stock fuel system is fine unless your running a turbo

Only OBDII cars use 4 02's, your running a ECU from a 93 Probe, it'll only recognise and use 2 02's. How old are yours anyway?

Your problem I would suspect spark. Disty/cap, maybe plugs, could be coil/ignitor.

[tbondo]

The O2's are not new by any means. The plugs and wires are new from the rebuild I had done. I cant guarantee that the plugs are gapped correctly since the guy that rebuilt the motor turned out to be an idiot. I guess I'll start by pulling a couple and checking them out. I know the disty is older as well. It seems to be functioning otherwise so is there a way to test it rather than just throwing money at it and trying things? Thanks

[crazycanadian]

The O2's are not new by any means. The plugs and wires are new from the rebuild I had done. I cant guarantee that the plugs are gapped correctly since the guy that rebuilt the motor turned out to be an idiot.

I think you know where to focus your attention with that comment...

guess I'll start by pulling a couple and checking them out. I know the disty is older as well. It seems to be functioning otherwise so is there a way to test it rather than just throwing money at it and trying things? Thanks

Yes there is but you need special equipment... Search my diagnostics thread and you''ll get an idea of what it takes...

Is it a really sharp/dead cylinder kind of ruff running? or more like a vibration slight miss here and there kind of ruff run? sounds like a possible vacuum leak/dirty fuel injectors/ timing belt out of alignment...

I run a Mazda 323 with a KLDE in it.. Using a 92 626 computer/maf from the same car... Headers 2.5" exhaust, intake.. Same set up with the O2's... Not sure what fuel pump but I am pretty sure its still the stock 4 cylinder one... I think you need a new mechanic to look at the car...

[tbondo]

Thanks for the direction. I will do some searching for your thread.

The idle is a vibration with a slight stumble now and then. Nothing real drastic. Seems to drive down the road okay other than the hesitation under heavier throttle and I also have a high RPM issue. These two together make me wonder about my distributor. My high RPM's are causing me to drive around town in 5th gear (~30mph). The engine sounds to be running at a higher RPM than it should be. That one really puzzles me. I've been told there is a difference between the RS (my original car and gauge cluster) and the GS cluster. Is this true? Could that be sending or receiving an incorrect message causing problems?

I have been thinking of bringing it up to a Mazda dealer, but would like to exhaust all avenues first since they charge $100 per hour. The rebuilder wasn't a mechanic. From what I found out after the fact is he does great engine machining work, but okay assembling. Wish I would have known that sooner.

[tbondo]

Got some new Denso O2 sensors ordered last night. Should be able to see if that helps the situation maybe next weekend.

[tbondo]

Was able to rule out the O2 sensors today. Got them installed, took a test drive, and the problems still persist. I guess next I'll have to do an inspection on the spark plugs.

[Daninski]

EGR can cause issues if it's not working correctly or dirty. Check all your plugs and gap to .041. For now put the car in diagnostics (TEN/gnd) and try adjusting the idle screw (top of throttle body) till rpm is 650 using a tachometer (not your dash one). Screw it in till the engine stumbles then back out till your running at 650rpm, then set the timing to 10deg.

[davmac]

I think you've solved your high rpm issue. The V6 requires a V6 tachometer in the instrument cluster like you'll find in a GS cluster. Daninski is sending you on the right path to solving these last few issues. Sounds like you've got all new "tune up parts" but now you need to do the tune up adjustments for this engine.

- set throttle position sensor TPS see manuals F2-152 and a few pages
- set timing and idle see manuals F2-73 and a few pages after
- verify spark plug gap and spark plug condition

If there are still problems you'll have to double check the usual suspects
- check ignition wires and make sure connections are solid and wires are clean and not shorting somewhere
- check the miles of vacuum tubing and especially that your cai is secure and not leaking air

Its the adjustments and details that are going to get you the last 2% to a smooth running swapped engine. Good luck.

[tbondo]

When you say idle screw I'm assuming you are referring to the one that is vertical and not the throttle stop?

[davmac]

Yes - follow the link and you'll get pictures and everything in the online manual. K8 or KLDE or KLZE the adjustments are the same. Idle adjustment is shown on the page 74 - just click on the first link and it will advance to the next page.

[tbondo]

Is there any way of adjusting the idle without a tachometer? I do not have access to one. The online manual lists some pretty specific tools that I would think most people don't have or have access to. Any other ways to do the tune up without these?

On a different note is there a difference in EGR's as in from the probe 2.5 to the mx-3 1.8? I don't see how the functionality would change from one car to the next. I am running the EGR from the 1.8 mx-3. I removed it a while back, cleaned it and check that everything moved freely. That seemed to be fine so I don't think that is my issue.

[davmac]

EGR is the same and will throw a code if there is a problem.

Assuming you have a working V6 tachometer in your dash you could set the idle using the tach in your car. It won't be super accurate but between 500 and 1K rpm is good enough for idle speed. Setting the TPS and timing requires a digital multimeter, feeler gauge and timing light - and a paper clip to put the car in diagnostic mode. If you plan on working on cars much these are a good investment. There's other options too. Talk to a neighbor, friend or relative that works on cars and might loan you these. Sometimes even these old cars can seem to be a bit expensive, but 1 or 2 uses of some of these tools and they will have paid for themselves in savings versus paying a mechanic plus you get to learn a bit about how the car works.

[tbondo]

Thanks for the direction. I do have a timing light, meter, and feeler gauges just not the specialty tools the manuals were referring to. I will have to work on it this weekend and report back my findings.

[davmac]

Sorry - misunderstood reference to special tools. You'll rarely need the Mazda specific special tools that are mentioned and the manual usually shows you how to do the adjustment or check without the special tool. You'll see that with every car brand and you rarely need to invest in the special tool that is mentioned. There are a few exceptions, but with a little imagination there is usually a way to do the same thing as some of these tools that have apparently been made for a specific car and repair. I have not bought a tool to work on the MX3 that couldn't be used on almost any car.