Hi I have low mileage mk2.5 1.8 vvt Auto here with major flat spot/hesitation between 2500rpm and 3500rpm only. Prefect when cold but once engine reaches normal temp hesitation is there. Previous owner said code P3302 did show diagnostic test but he cleared fault. No codes showing now.Its AUTO car so impossible to drive with this hesitation. I fitted air flow meter, temp sender switch at back of engine,. Hesitation is not electrical breakdown, its vacuum, vvt maybe or similar.If I hold revs at rpm car is “hunting” up/down/up/down.I also swopped ecu as temp check but car still the same issue. Previous owner thought car smelled overfuelling when behind. Cat blocked maybe? but then why is it perfect when cold? I am bit lost with this one so any help appreciated. Thanks
This car may have VCT controlled inlet butterflies?? not sure so maybe that’s the issue?. or can inlet manifold be exchanged so earlier type?
ITS EX UK CAR REG D9MMW??? WITH 45K SHOWING ON CLOCK??
Update. OK . I removed the later VCTS inlet manifold and replaced with older VICS ? manifold from 1999 1.8 mk2. Still same issue only now I have discovered that if I remove the Throttle Position Sensor connector car runs fine , only that its slow to accelerate . The hesitation is gone with connector removed. Tried refitting connector and original problem comes back so definitely TPS related. Do the TPS have to be calibrated to car?? or is it just matter of bolting it on with throttle closed?Robert
Ok, Anybody out there?? update. Swopped another throttle body, TPS, front qxegyn sensor, vvt selonoid, . No fault showing on OBD, car still hesitant between 2500-3500rpm. Runs fine with TPS disconnected but no real acceleration, very flat to drive obviously but no flat spot,. Cleaned EGR valve. I had multi meter on TPS and getting 5v power, ground and up to 3.7v. WHEN TPS NOT ACTUALLY ON THROTTLE BODY. (using second TPS, for testing purposes) but when TPS is fitted to car signal is low voltage. This is one for the real lads who are good at problem solving. I also fitted working ecu, immob, key set but no change in car, just in case ecu fault.
Checked with Mazda and they advise TPS part number BP2Y 18911 A but the A part seems unusual as I have several AUTO tps units here and none have the A at end?? Is there a difference? Even the original TPS did not have the A at the end? but may have been swopped beforehand?
My next thing to check is Crank sensor or mad idea that the crank wheel/plate may be damaged but then car would not run well when cold. I did fit new coolant temp sensor unit last week.(3 pin at back of cyl head) Long shot.
Roadster Robbie may be able to help? thanks
The A on the TPS is to indicate a superseded part. You can fit a part with an A in place of a part without an A.
Sounds like a TPS issue to me if the fault disappears with it disconnected. Maybe a wiring fault if you’ve tried a different sensor. What readings are you getting from it exactly?
Hi. 5volt supply. Ground on black .and up to 3.7v as throttle opens fully but only when ignition on. With car running all as above but max maybe 0.7v to maybe 0.9v and large gap then until maybe 3v onwards. Cant understand why while engine running should be different to only when ignition on. Weird. Constant 5v supply and ground regardless of ignition on or car running. Why should having engine running make difference. Swopped to two other tps without the A and still same issue. Also swopped ecu. Airflow. Alternator. Coolant sensor. Egr.throttle body.
Hi Robbie. I can call you if you text or whatsapp me your number. 00353 86 8226506. Thanks. Robert
I ordered a variable dimmer type switch from ebay. Going to try separate 12v supply and reducing it as test only.basically individual 12v supply from separate battery, reduced by dimmer,
I also swopped cam and crank sensor but still no improvement. Runs fine when car is cold but hesitation once temps reach half way on dash. Runs fine with tos disconnected but no timing advance etc so very sluggish to drive but no hesitation. Its Automatic box so needs to be running correctly. TIA.
I am getting desperate. I can whatsapp you video if that helps.
What’s the VIN of the car? From what you’ve described I’d be tempted to cut to cut the signal wire from the TPS to the PCM and run a new wire in. I’m thinking is there a short from the ECT sensor wire to the TPS wire? With a VIN I can see if they run in the same harness to see if that’s a possibility.
Jmznb18p500214510. Thanks
The Green/Black wire from the TPS goes straight to the PCM through the Emission harness. The Red/Blue ECT sensor wire also runs through the Emission harness. The Emission harness is the one that the ignition coils are on. What’s interesting is, as the car is an auto, splicing into the Green/Black wire from the TPS is another Green/Black wire that runs off to the transmission control module (TCM). This wire runs through the Emission harness before joining the Front harness at the blue connector X-04 which is behind the dash. The TCM is located to the left of the steering column and should have 1 large block connector in it.
Maybe try disconnecting the TCM and seeing if the fault goes away, failing that I’d start checking wiring.
Hope that helps.
Hi robbie. I will try disconnect the TCM harness as I know it’s near where clutch pedal would mount normally. I may even have another spare tcm if needed.Though you were on the something there with tos wite shorting with temp sensor. I might try cutting tps wire and running in loose one. Fair play to you for your help and efforts. I will update later today. Fingers crossed otherwise its breaker job but lovely car. Too good to break. I did several auto to manual swop but dint think that would solve my problem so no point yet in doing that. Unless it auto loom fault as you say. Thanks. Top man.
Just spoken to Rob about this - gets confusing as now three of us involved![Smile]( "Smile")
The auto car is running a BP6M manual ecu. From my experience replacing the auto BP6P ecu with a BP6M will start the car and it will run but it then hunts. Unfortunately been there and done that with a garage customer on the Channel Islands.
I disconnected TCM but no better. ECU has part number bp6m which I fitted as car already had bp6m but turns out it should be bp6p? for auto car. I am trying to contact previous owner to check did he swop it already before I got the car. Car was in several garages apparently for same hesitation issue. That’s why I ended up with it!! Fingers crossed I get old ecu kit but unlikely . Might have to convert to manual box. No big deal really. Done 4 before so I know what’s involved. Lifes a bitch!!. Would not having the auto box control box not eliminate the need for bp6p ecu then?
Hi. I also did cut the tps wire at throttle and ecu earlier and ran loose wire but no better.just in case it was shorting in loom.
Did you check the voltages again with the temporary wire in? Have you tried running a new earth for the TPS in?
Yes tried separate earth to tps ground. Voltages same but car has bp6m ecu and advice is should be bp6p for auto. Rhino etc confirmed ecu is incorrect
I had fairly obvious flat spot when I first bought my nbfl.
After reading some interesting posts on the subject, I switched to shell, which apparently has better engine cleaning additives than say supermarket fuel. Runs much better now, but took a few weeks to kick in. Might be worth a try.
Just trying to think laterally…which I’m not especialy known for!
The car runs OK-ish cold whilst the what I would label “ECU enrichment mode” is in operation, then temp sensors tell the ECU to back off, and as required the injection system runs “lean”?
Any clues there?
Additionally, we too had a hestitation/flat spot on our 2002 Sport which caused a lot of guessing until I gave up and fitted new coilpacks…solved. This also happened only when the auto-rich was off and the engine’s bits got hot.