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96 mazda b2300, starts easy, rev's good in neutral, no guts at all when driving. timing is good, catylatic converter good, no differenct with or without exhaust. swapped mass air flow sensor....no change in power. only gets to 50 mph. got any ideas??
1996 Mazda 4 cyl 2 wheel Already Tried: new timing belt, timing verified correct, caty converter, clear exhaust, new mass air flow sensor. took to ca. smog mechanic to run test. there are no codes on OBDII everything looks good but truck will not go faster than 50 mph and takes awhile to get there....
Hello! I'm Rixster...
If you know the Exhaust is not plugged anywhere then I'd start looking at what feeds it.
Is the Vehicle getting proper Fuel Pressure? There is a test port on the Fuel Rail and you will need a good Fuel Pressure tester to check this.
Pressure should be... About 39-40 PSI while running.
also check your Fuel Filter for being resricted...
Let me know what you find.
I Hope this helps...
Thanx! -Rixster
good thought but .....fuel pressure is also good i forgot to mention that.
look for water in the fuel or did you fill with e85 fuel?
Well It's rather Obvious this new expert feels the need to have this question so I'll let him run with it.
Good LuckCustomer
There was some old gas in the tank...less than 1/4 tank 4 to5 months of setting.....so I topped it off with premium 91 octane and added a little "Berryman" carb/injector cleaner. I put some fuel in a white container when i checked the fuel pressure...fuel was clean and no indication of water. fuel filter does not seem clogged
Well It doesn't look like the other guy had too much to tell you so in the interest of taking care of a customer I'm opting back in...
So the Fuel sample was good! The Fuel Pressure is good! and you are sure the timing is right correct? "New Timing Belt"
MAF Sensor is ok?
No Codes?
We're missing something!
Pull the Fuel Filter and try to blow thru it. If there is any restriction at all replace it.
Make sure of your exact Fuel Pressure (39-40 PSI)
Anything else been done recently?
Well let's see now i have checked fuel pressure again and the fuel filter both good, I took the truck to the smog shop and they verified / re-did all of the test that i have already done. they also ran the truck on a dyno smog tester and the mass airflow sensor reads 10,000 alt ... i'm only at 2000 alt so i put a new mass air flow sensor in still no joy. No change in the reading. Smog shop hooked up a new computer ECU......and that did not help either. Smog shop had the truck for three days checked Catalytic converter and exhaust but they also said the exhaust flow was not clogged. Everything checks good on the OBDII, the truck starts easy, idles smooth, reve's smooth in neutral and in gear but has very low power.....rpm stalls at 3000-4000 like its not getting the gas to go any faster (still 50/57 mph max) but fuel pressure is good.
Then we need to look at timing! Make sure your timing marks are lining up correctly. The Timing cover comes off pretty easily and would be well worth the look.
Also (just for assurance) check for any type of air intake restriction. Throttle Body and Plate condition.
You might consider doing a compression check too.
Wanna see reasonably similar results across the cylinders and above 100 PSI Minimum of 70 PSI (which would be considered worsrt case)
I know you are trying to get this going and I apreciate the info you've conveyed.
Thanks for the vote of confidence but this thing is kicking my butt.....However i don't give up Today it started acting a little different. worst actually..... but at least we have something to work with an While in Neutral the rpm will rev smooth to 3500 and then drop off like its going to die. if i release the throttle it resumes a smooth idle.........does the same thing while driving, and if i hold the throttle at 3000 plus it will fluctuate from 2900 to around 3200rpm Driving 1st gear is good, 2nd is ok but slow to build rpm and when the RPM reaches 3500 or so the power drops off again. I ran the truck as fast as it would go in 4th gear (pedal to the metal) to get the rpm up to 3000 and then down shifted to get the rpm above 4000 (engine breaking) and it worked for a couple seconds rpm held at 4500 or a little more..... then the big "power drop" hits again. Something is telling it to drop off or not letting it speed up..... just a guess but where/how does the timing advance work on this thing. it reminds me of an old distributor with a stuck advance plate. what do you think? Oh yea the timing marks are spot on.....I changed the timing belt so thats the first thing i thought i might have screwed up. but i double checked the marks and also had the smog shop do a dynamic check.....the marks lights up spot on the money. still need to check compression but it starts easy and is real hard to crank around by hand with the spark plugs in .
I agree with you it's got to be timing related. There really is nothing else.
The advance is all done by the processor in the PCM. It receives signals from the Crank Sensor and Cam Sensor and adjusts according to engine load sensing via the Mass Airflow and O2s You might try to locate a good used PCM and swap it out just to see if something is up there.
swapped out the PCM with a "good used one" the truck would not run at all...i couldnt even drive it around the block..........put the original pcm back in and it starts and idles fine, but rpm is still held up at 3000 to 3500........i guess i'll have to go to a Ford Dealership to get this one figured out.......... Thanks Marc
It Obviously was not a "good used" PCM Good Luck My Friend!!!