My 2000 Protege DX, 1.6, 5 speed, 117,000 miles bogs on the subtlest of inclines. On a level or down hill road it runs like its normal, underpowered self. But even the incline of a freeway on ramp causes the car to bog like I am one gear too high for the conditions (even though its not). This has occurred almost undetectable over time. It is not something that just started one day.

There is virtually no torque out of the motor and acceleration is extremely slow until about 3,000 RPM. From 3,000 RPM onward the car accelerates like it should and at about 4,000 RPM acts like a carbureted engine with the secondaries having opened (the power picks up considerably). This is driving me nuts.

For the record, the car recently passed a California smog check which loads the engine on the dyno. The results across the test ranges were only about a third the way to the limit. This does not seem to indicate any engine problems. The car has NO codes (and never has). It idles fine. There is no miss. It doesn't really stumble either. It just bogs until it approaches 3,000 RPM.

The air filter (Wix) and plugs (NGK) are new. The timing belt I replaced about 15K ago. There are NO air leaks. I replaced the large MAF to throttle body hose a while back. The O2 sensor is new (Denso). I removed the fuel filter and found it immaculate. I did find some minor "slime" around the fuel pump inlet and removed it. I also flushed the pump and while having no official pressure test it did flow exceptionally strong to the eye and finger. Even though the MAF looked clean I used an appropriate cleaner on the elements. None of these replacement items/ fixes changed anything.

Since the car idles fine - and will accelerate normally from about 3,000 RPM to the redline there is no indication that fuel/air delivery, spark, or a clogged CAT/exhaust are the problem. If those things are at issue the car would be incapable of that. Also an air fuel ratio issue would have shown up in the smog test that was easily passed.

So, I'm baffled because acceleration (on an incline only - be it ever so subtle) is mercifully slow until about 3,000 RPM. And sadly virtually every "natural" shift point (the 1 to 2 shift being the worse) drops the RPM to around 2,000 RPM. Then it struggles back up until 3,000 RPM. I have to wind the motor up to 5,000+ RPM - then shift (dropping closer to 3,000 RPM) to have any hope on inclines. Once I crest the smallest of hills everything is fine again.

I've looked around on Mazda boards and there are others with the same complaint. So, I know it is just not me. However, there are really no answers either. Anyway, hoping for direction. Thanks for reading my problem. Tom

 

I am not familiar enough with the 2000 Protege to give a definitive answer. However you did not mention the Throttle Position Sensor, nor the PCM, nor the ECT sensor in your process of elimination.

 

Mazda extended the warranty on the MAF for years 99 and 2000 for poor driveability complaints, Sometimes a check engine light but usually not. Check the rubber boot from the aircleaner to throttlebody for cracks,clean the MAF and throttlebody. It is probably a bad MAF though. Can't say for certain without the car in front of me though. The MAF has 5 numbers/letters on it. XX X XX if the center is a T U or a B it was produced in 1998/1999/2000 and is likely a bad one.

 

Thanks, as stated above (buried in my detailed account) I had already replace the hose you spoke of. And, though I didn't mention it, the throttle body was also cleaned. I looked into the MAF Warranty and it is only good for 7 years/70K miles. So, I'm 7 years too late and 47K miles too far down the road for that.

Thanks for the MAF numbers. I checked and the number is 07B28. So, it seems likely to be the problem. By the way, the Rock Auto Denso number is 1976020 but the MAF in my car is a 197400-2010. Should I be concern? From what I'm seeing this is a MAF for a 2.0 engine not a 1.6. (Update) Just found someone who has the number I do on a 1.6 "Latin America" Protege.

I was thinking MAF but at around $100 I was hoping not. Any of the lesser costing MAF's you would recommend? The Denso is $75 at Rock Auto. Even a rebuilt has a $50 core charge and my favorite Pick A Part wants $35 plus a $5 core. But I'm not going that risky. I also checked a cross reference and the same MAF was used on a lot of Mazda's and Lexus/Sion (Toyota's).

One last thing, when I replaced the hose I don't recall resetting the ECU. I just now pulled the negative cable. Tomorrow I'll reconnect and will see in the morning drive if it did anything. A last hopeful attempt before I purchase a MAF.

 

I took a two way 100 mile trip today that included numerous hills. I would say the car is somewhat better. Where before if I encountered a hill and pressed the accelerator I got nothing or lost momentum. Today I seemed to maintain or slightly see a speed increase. Also, in town shift points didn't cause the car to struggle for momentum as much as before, but it still only had just a small level of acceleration. So, I think resetting the ECU helped, but I'm not sure it is a fix all. I'll give it a week or so. The wife is due back next week. Between she and the baggage it should add enough to weight to notice a difference. Before even my 105 pound daughter in the passenger seat made the car noticeably slower.

I miss the torque curve of my old 1991 323. It was MUCH better for average overall driving. I went from 165-70-13" to 185-60-15" tires and the car never really noticed the size increase. If I did that to the Protege it would bog like crazy even without the problem I have. The newer motor really has nothing until 4,000 RPM. And, for normal driving that is a shift point not an operating RPM. Anyone ever alter the cam timing to move the torque curve lower?

 

Are you 100% certain you have the timing marks all lined up correctly after replacing the timing belt? Even 1 camshaft being 1 tooth out will run fine and feel ok around town.

Just something to double check.

 

I agree with Grim_Reaper. That engine has 2 cams,the camshaft position sensor only reads timing off of 1 cam and will set a code for cam/crank correlation if it is out of time. If the other cam is out of time it will not set a code. Those are super easy to get out of time. Removal of the upper timing cover will give you access to check it. That engine should have plenty of power. A partial exhaust restriction will also cause what you describe, a CKP on it's way out will also cause it. Excessive carbon accumulation on the valves will starve the engine too. A couple bottles of Techron run through it should clean the carbon issue up if so.

 

For sure I know the belt was installed correctly. I always mark all three pulleys and the belt with three different colored paints. Then I transfer the the paint marks to the new belt. I have found this far more reliable than what at times can be ambiguous indicator marks and the angle one can sight them at.

I agree that my situation is indicative of an exhaust restriction with the exception that once above 3,000 RPM it responds well to full throttle input.

I did have an issue a while back where I was intermittently getting a P300 Random Misfire code. But, only on the few times I used the A/C. Turned out that the crank bolt was loose enough to cause the balancer to slip, but not enough to feel loose when I felt it. Eventually it worked loose enough that it sounded like a rod knock. I retightened the bolt and it went away. Now I'm wondering if the rocking back and forth altered the key and or the key slots to shift the timing off??? It may be tight..., now, but is it retarded in relation its intended position due to key/keyway slop?

 

It is possible to waller the keyway out enough to throw the timing off. There is no substitute for the factory timing marks. If your belt was worn your marks might be off with a new belt. It sounds like you need to remove the crank gear to check the key anyway. I can't stress enough how easy it is to get the timing off on those cam gears. When I do one I turn the crank 2 full turns and check the marks again. Faliure to do so can cost you time doing it over again.

 

Yes, I am well aware that the cam lobes can cause the cams to snap left or right (rotationally) when the belt is loosened. But, the timing relationship is based on a tooth count. That is why I mark the pulleys and belt and then transfer the marks to the new belt. I am meticulous about it (checking three times) and ensure that they hold after the belt is tensioned and that there is no slack on the "pulling" side. I've done at least 10 timing belts this way and it has never been a problem.

Also, the belt was replaced over 3 years ago at 95K*(below). The engine now has 117K and it has only been in the last thousand miles or so that this issue creeped up. When I initially replaced the belt it was not a problem, - then and for another 20K miles it was not an issue.

I only drive the car a few times a week. So, it will take a few more drives to convince me that the EPU reset made a significant enough change. If not I'm incline to think the MAF (of questionable integrity - it has a "B" center letter) with 117K miles on it is the culprit. Thank you for all your replies.

*I always replace belts at 60K but I was not the owner of this car until 95K. Thankfully the belt held up better than the spark plugs (also with 95K on them). The electrodes had worn to the point that the gap was approaching .090!