2002 Protege DX Stumbles...No CEL

YenkoZL1

Member
:
2002 Mazda Protege DX
2002 Mazda Protege DX Automatic, 95k Miles, Stock with 600 watt sound system.

Recently did an Oil/Filter change and serviced the transmission w/ Filter and Fluid. Washed the vehicle today and sprayed down the engine bay. On the way home I was slowing down for a red light which turned green before coming to a stop and at 25mph I went to accelerate and the car stumbled slightly to the point where it seemed like the transmission was searching for the correct gear to down shift to. No issues after that until I got home. The vehicle was in the drive way at idle with the a/c on and it stumbled to the point that it ALMOST stalled and then recovered. I let the vehicle cool off for about 1hr and then went out to take a look at it.

I started with the voltage and used my Midtronics Battery/Alt/Starter Tester. Initially the vehicle stalled after about 10 secs of running when cold. Started it back up and everything ran like normal. Voltage wise everything checked out good. CCA - 820, Battery Voltage 12.86v when vehicle was off, Volts to starter 11.50v, Idle amps prior to accessories 14.4v. But, I noticed with the A/C on Max, stereo was on at listening level while driving, and head lights on, the voltage AT IDLE would drop to 12.53v from a slow bleed off from 13.4v. If I gave it some gas the voltage would rise telling me the alternator is working. I did this test because the Alt is Original.

Once I turned off the A/C the vehicle would then start to stumble and recover repeatedly. Voltage was at 13.46v during the stumbling, then recover.

Curious what this could be? No Check Engine Light.

Parts replaced within the last 30k mile or less...

Spark plugs/Wires - AC Delco
Ignition Coils - Beck Arnley
Fuel pump - Mazda Geniune
Fuel Pressure Regulator - Borg Warner
EGR Valve - Borg Warner - with updates
PCV Valve - AutoZone
Timing Belt/Pulleys/Tensioner - Contenintal( yes like the tire co.)
Water Pump - Mazda Genuine
A/C Compressor - Hitachi
Battery - Optima

At this point I am leaning on either the Coil packs AGAIN, or the speed sensor in the transmission - Possibly

Any pointers would be great
 

YenkoZL1

Member
:
2002 Mazda Protege DX
UPDATE -

I test my coil packs and the resistance in Kila Ohms is a little high...roughly 13.3 Kohm Shouldnt be higher than 10.52 kOhms via Shop manual. High tention leads look good and test very well. Spark plugs look good, no carbon build up or greyish coloring but there was some orange coloring slightly. Maybe an enrichment issue? So I replaced the coil packs and plugs. Start the car when it is completely cooled down and nothing happens until it is completely warmed up. The rough idle continued whether the a/c was on or not. The car actually responds to the a/c kicking on and increasing idle like it should and when the rough idle kicks in its not as bad. Once the a/c shuts off the vehicle tries to die but compensates and keeps it running. At this point since the rough idle did not start until it was completely warmed up I am thinking it may be the EGR....But still no CEL and it damn near died.

I ran a dianostic w/ my OTC Nemisys and no codes popped up and I ran a real time diagnotic but nothing is jumping out at me. I will test the Turbine Sensor located on top of the tramsmission under the air filter once it is cooled off.

EGR Position was at 0 when in park and at idle.
IAC was at 13%-15% range.
MAF - 2.11v
Coolant Temp - 1.43v

If any of this info jumps out at you please let me know....at this point I am looking for any ideas. We can Volley back and forth until something clicks? :)
 
Last edited:

YenkoZL1

Member
:
2002 Mazda Protege DX
UPDATE

So last night I took the car for a test drive and it wouldnt move out of its own way. Give it a little fuel and it would fall on its face and this time it stalled out twice. Still no CEL. The car will fire right back up w/out issue.

So, what causes a vehicle to have a rough idle and stall while driving and not throw a CEL?

I only have 2 guesses..... Vaccum leak or MAF.

In my previous post the voltage at idle of the MAF is 2.11v. The range should be 1.7v - 2.4v - but I am not sure if it is bad. It was replaced maybe 10k miles ago brand new from Standard.
So far I cannot locate any vaccum leaks. Other parts that are original are the EGR Boost valve, and Purge Solenoid.
Alot of parts have been replaced due to the infamous P300 code a few years back. :)

So nobody has expierenced these problems with their Proteges?
 

YenkoZL1

Member
:
2002 Mazda Protege DX
I did some more resistance testing today. As of now the IAC and the TSS are testing out well. The only thing is that the TPS sensor tested at 1.37 Kilohms.... shop manual says resistance should be 4-6 Kilohms. Anyone think that by it having less resistance than it should per the manual be an indicator that it is bad?
 

MaxPower

Member
:
'01 Pro ES
Did you check the accordion intake tube for cracks? You should remove it to properly inspect it.
 

MaxPower

Member
:
'01 Pro ES
That's odd that the TPS has such a different resistance from spec. Any way you can swap in a good one? Maybe get one from a junkyard?

Other thoughts: purge solenoid valve, cam sensor, crank sensor, low fuel pressure.
 

YenkoZL1

Member
:
2002 Mazda Protege DX
I went and bought a new TPS today - Borg Warner. I would think that if the resistance was less there wouldnt be a problem but at this point I am going by what the Shop Manual says. The purge solenoid will be my next train of thought if the TPS isnt the issue. The cam and crank sensors are magnetic. So for those to fail I would think there would have to be a short or possibly corrosion at the connector or missing a tooth on the timing gear. And I would hope it would throw a code if it wear either of those. The connections look good and I recently replaced the timing belt maybe 10k ago and there were no signs of abnormal wear. Once I get everything back together I will check fuel pressure. The pump and regulator was replaced recently as well b/c of the infamous p300 code I thought for sure it was that because the way the vehicle was running in limp mode and having 76k on the car. So if it is, the part should still have some kind of warranty from Mazda since I purchased the part there.

Thanks for the replies I appreciate it. I will let you know after today what happens.
Vehicle has a rough idle hot or cold, a/c on or off and will stall if driven, yet no CEL. It has to be vaccum related.... Im just not finding any signs of where.
 

MaxPower

Member
:
'01 Pro ES
That's pretty frustrating. At least the problem is reproducible, so you'll be able to track it down. I agree the crank and cam sensors are unlikely. Does sound like a vacuum leak. Other thoughts:
-Did you try disconnecting the IAC valve (the car should stall)?
-Did you check the Long FT1 PID (can tell you if engine is running lean or rich, which will point to vacuum leak or emissions problem)?
-You can try plugging the vac hose from the purge solenoid valve to the intake manifold to see if the valve is faulty.
-I know the new EGR is claiming it's closed, but if the valve is stuck open, it will cause a big vacuum leak and might not throw a code. Worth inspecting, especially if the rough idle started after the engine warmed up.
 
Last edited:

YenkoZL1

Member
:
2002 Mazda Protege DX
Installed new IAC and TPS, started the car up and purred like a kitten when cold. At 190 degrees when warmed up the rough idle came back. It seems to be better than before but I am not certain. Phx, Az is at 1120 ft above sea level so my vaccum shoudl be at like 17psi to 19psi. I am pulling 17psi at the intake. When the rough idle comes back it drops to 15psi. So I am pretty sure I can rule out a vaccum leak at this point. Since the rough idle doesnt kick in until the vehicle is completely warmed up I am thinking it is an emissions issue. If it were the fuel pump, or a vaccum leak I think it would have shown itself instantly when the car was started cold. I need to find out what my fuel trim levels should be and look at that. MAF voltage is running within specs. Grrrr. :)
 

YenkoZL1

Member
:
2002 Mazda Protege DX
My up stream and down stream O2 sensors are giving me a couple signs. Operating range is 0.5v - 1.0v. Anything below 0.5v is considered an enrichment issue. Anything way above means a lean issue. So, my main upstream O2 sensors is reading 0.2v and will slowly adjust to 0.3v at idle. While my rear stream is idicating 0.46v. Hmmm....can an O2 sensor go bad and not throw a CEL? I dont have a major exhaust leak and nothing is shown and intake manifold leak that could throw off the O2 sensor. The main stream O2 sensor is stagnant when you accelerate. I wouldnt think it would be. And I was under the impression that O2 sensors would not cause major drivibility issues. Excessive fuel usage yes, but shouldnt cause a car to run rough and stall? Could it? The fact that it is way out of range is concerning. But why would there be an enrichment issue? MAF tests out very well, electronically and when you do the ole' tap on it trick.

The car runs perfectly fine when cold but once its warmed up it starts to act up. Maybe the O2 sensor is the issue?
 

YenkoZL1

Member
:
2002 Mazda Protege DX
Correction to my previous post......being that my O2 sensor is reading 0.2 - 0.3v this would indicate a lean condition, not a rich one. So, the scale is 0.0 - 1.0v, 0.5v idle a/f ratio andything above is considered rich, anything below 0.5v is considered lean.
 

YenkoZL1

Member
:
2002 Mazda Protege DX
So, I replaced the main up stream O2 sensor in the manifold for good measure. The old one was pretty stagnant which is a sign that it could be bad. They should fluctuate 20-30 times per minute and mine definately wasnt doing that. And being the car was idling so rough I thought for sure it would be pretty active...And it wasn't. So, the new one did not make a difference in idle. However, it was responding and fluctuating like crazy BUT, this time it was indicating an enrichment issue being it was flucuating from 1.3v to 1.43v. So, I dunno if I did myself any favors by replacing this item of if its just another case of me throwing parts at the car. Which I hate doing but since there is no CEL I am totally in the dark. The rear O2 sensor was still idicatng 0.46v which is pretty ideal. So, am I truely running rich or lean? If I was lean, then this could mean Fuel pressure issues, but rich? Plugs are clean and golden brown. Coils are new, so I dont think I have a spark issue.

Literally the car was running perfectly and all of a sudden the idling issues came out of no where and the stalling too. I will be looking at the fuel pump next. I have not touched the car yet today so, if it starts up and run fine while cold then I am still at a loss, b/c if it were the fuel pump or Injectors I would think the symptoms would be present regardless of vehicle operating temp. But, I am sure I am wrong b/c I have been so far this whole time. :)

Fuel pressure testing today at the tank and then at the manifold.

Car starts up fine everytime it stalls. I hear the pump prime and then it fires right off like it should. It just cant stay running. I wonder if the fuel hose in the tank that connects to the pump has a crack in it that is preventing the pump from holding pressure consistantly.
 
Last edited:

MaxPower

Member
:
'01 Pro ES
Wow, this is a challenge. Have you checked for any codes recently? Maybe one is pending, but hasn't tripped the CEL.
 

YenkoZL1

Member
:
2002 Mazda Protege DX
Still no codes or pending codes......Waiting on some items for my fuel pressure tests. As of now I am checking voltage at the pump to see if I can read whether or not the pump is starting to go bad. I knwo that sometimes when the temps get to a certain point it can mask a bad fuel pump. Which is probably why the car runs perfect when cold and once at operating temps it starts acting up.

The pump works. I hear it working when priming the motor before start up and when running I can hear the pump operating. BUT, I might have a continuity issue with the harness connector for the fuel pump housing. Its the square connector that attaches to the top of the fuel pump housing. I tested the prongs sticking out of the housing and there is continuity with all four prongs. HOWEVER, when I go to test the connector for the harness I get no continuity what so ever. Not sure WTF is going on. Maybe I am not getting a good enough connection but the pump works when everything is connected. I am afraid to jam my test leads into the connector b/c the connectors are kind of like a compression fit and I dont want to strech it out. Make sense? No corrosion on anything, and evrything fits nice and snug. The ground side of the connector harness seems to be a little worn, and the tabs appear to be compressed more than the hot side, but it isnt concerning...Well, not yet... lol

Any ideas?
 

YenkoZL1

Member
:
2002 Mazda Protege DX
The plug wires are fairly new, with maybe 12k on them. I inspected them and tested the resistance and everything is in spec. Still look like new and sign of any damage or wear.
 

YenkoZL1

Member
:
2002 Mazda Protege DX
-Fixed-

Well, it ended up being the FUEL PUMP. The pump would hold pressure at 22 psi for 5min plus. BUT, when constantly running while vehicle was idling it would slow down or get weak. Pump had maybe 25k miles on it. It was a Denso too. Tank was clean, strainer was clean no sediments. Hopefully the new pump will last longer than 25k miles.