Start with a compression check just to make sure your motor isnt the problem, let us know what the numbers are, should be within 10% across the board. I believe it should be around 140psi if I remember correctly.
Any ideas on what could cause a low rpm hesitation?
I have a 98 Tacoma 2wd 2rz with 196,000 and i'm having a low rpm hesitation, stumble. I have recently replaced the fuel pump and filter, sparkplugs and it has older msd wires on it. Any ideas? sorry if this has already been posted, I couldn't find anything!:brickknoc
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Personally, I'd replace the old ignition wires first before I went as far as trying a compression test.
Did you have the low-rpm stumbling before the recent changes, or not until after them?
If you do go ahead with the compression check, the key numbers are:
- GOOD = 178 psi or higher
- MINIMUM ACCEPTABLE = 127 psi in any cylinder
- MAX RANGE OF VARIATION among cylinders = 14 psi
Did you have the low-rpm stumbling before the recent changes, or not until after them?
If you do go ahead with the compression check, the key numbers are:
- GOOD = 178 psi or higher
- MINIMUM ACCEPTABLE = 127 psi in any cylinder
- MAX RANGE OF VARIATION among cylinders = 14 psi
Watch out for water getting into places it shouldn't be like wiring or ecu
If all the above doesn't work maybe cleaning the idle control valve?
That's another 'likely suspect', and it's another thing that might be wise to do before going to the trouble of a compression check. :thinking:If all the above doesn't work maybe cleaning the idle control valve?
trouble of a compression test? no to impede on your infinite wisdom randy, but that's a 15 minute job:shrug: and will give you more definite answers than spending money on plug wires.. and its easier than cleaning the iac
Good point, Chris, but ... All I meant was that unless the engine has been in obvious 'decline' it's more likely this immediate stumbling issue is caused by something 'around' the engine rather than the engine itself.
very true, however i use a compression test as a base for my diagnostics on engines.. start from the most basic ie. compression and rule that out instead of chasing my tail further down the line..
To answer a few questions, yes it was going on before the new parts then got better for awhile now coming back and getting worse! It's also strange because it doesn't do it all the time, run's just as good as always after about 1500 rpm. I have also cleaned the MAF as hear K&N filter oil can mess with them. Could a bad O2 sensor cause it? It feels like it's the gas surging or cutting out, I'm not sure that it's compression cause like I said it runs just fine after 1500! Thanks for the help any more Ideas would be greatly appreciated, I'll get back to ya'll on the compression though! :waytogo:
Fuel filter ? Are you gettin cel ? If the pull the iac wires off when it's running to see if there's a change at idle I did that found out it was the iac valve
i agree with cleaning the IAC...cant hurt even if it doesnt fix it.Fuel filter ? Are you gettin cel ? If the pull the iac wires off when it's running to see if there's a change at idle I did that found out it was the iac valve
or a vacuum leak somewhere, causing it to stall/surge at an idle, do you hear any kind of leak? i had a broken vacuum line once and it made the truck idle like sh!t, but would run fine when driving.
i would not think compression would be an issue, if its not blowing smoke, then chances are it has compression...
check the gap on your spark plugs.
buddy of mine has a '97 3rz with dual coil packs... had a low rpm studder and we could not figure out what it was. turned out to be that the spark plugs were gapped too loosed... tightened 'em up and the studder disappeared.
buddy of mine has a '97 3rz with dual coil packs... had a low rpm studder and we could not figure out what it was. turned out to be that the spark plugs were gapped too loosed... tightened 'em up and the studder disappeared.
i agree with cleaning the IAC...cant hurt even if it doesnt fix it.
or a vacuum leak somewhere, causing it to stall/surge at an idle, do you hear any kind of leak? i had a broken vacuum line once and it made the truck idle like sh!t, but would run fine when driving.
i would not think compression would be an issue, if its not blowing smoke, then chances are it has compression...
Untrue, a low compresion motor will not smoke due to compression loss, it will smoke due to bad valve seals or piston rings.
Just so people dont get misinformed.
I start with a compression test because you want to be sure your motor is fine before you get into the rabbit hole....only takes a few minutes.
I do this stuff as a profession all day long and I would say it is beneficial to start there just so you know if nothing else. If you didnt do that and it was the problem you could spend tons of money and time trying to diagnose a problem you missed.
Dont you want to make sure your pump (motor) is good before you check the little stuff? If there is low compression nothing else matters, my .02.
im not arguing just curious, what else could cause low compression? in a bascially normal common situation...[/color]
Untrue, a low compresion motor will not smoke due to compression loss, it will smoke due to bad valve seals or piston rings.
Just so people dont get misinformed.
I start with a compression test because you want to be sure your motor is fine before you get into the rabbit hole....only takes a few minutes.
I do this stuff as a profession all day long and I would say it is beneficial to start there just so you know if nothing else. If you didnt do that and it was the problem you could spend tons of money and time trying to diagnose a problem you missed.
Dont you want to make sure your pump (motor) is good before you check the little stuff? If there is low compression nothing else matters, my .02.
bad head, head gasket rings or cylinders, i think that all of these would cause pretty bad symptoms other than a surge at idle...
I have seen bad idle due to low compression because the IAC is trying to compensate for a crappy idle. Happens..
After 150,000 miles some 2/3RZ motors start to loose compression due to the valve seats and valves not sealing, as a matter of fact I have done 2 2RZ head jobs in the last 3 weeks for the same problem, although this is commonly causing a CEL of a cylinder misfire.
Low comp usually causes idle problems, but after 2000rpm or so it is fine because the engine has inertia helping it along.
This may not even be the problem however a comp test is never a bad idea.
Wasnt jumpin on yer sh!t man, just sayin..
After 150,000 miles some 2/3RZ motors start to loose compression due to the valve seats and valves not sealing, as a matter of fact I have done 2 2RZ head jobs in the last 3 weeks for the same problem, although this is commonly causing a CEL of a cylinder misfire.
Low comp usually causes idle problems, but after 2000rpm or so it is fine because the engine has inertia helping it along.
This may not even be the problem however a comp test is never a bad idea.
Wasnt jumpin on yer sh!t man, just sayin..
i understand the valves not seating, but if they arent seating, i would THINK that it was cause it to run like crap through all RPMS....not sure, never had real bad valve issues
i understand the valves not seating, but if they arent seating, i would THINK that it was cause it to run like crap through all RPMS....not sure, never had real bad valve issues
Negative, when driving it is possible you wont even kow the valves arent totally seating, until it idles.
I'm getting ready to replace the EGR on my friends truck, she has the same symptoms. After about 1800 rpm it runs smooth as can be. but under that after its warmed up it shutters and sometimes loads up so bad it wants to stall out. Luckily it threw a code for the EGR performance (p0404) and another for EGR position (p0405) cause otherwise I would be doing a fuel pump and filter and all that too.
Thanks for all your help! It would seem it is the IAC! I still haven't checked the compression, but unplugging the IAC has seemed to help alot! in regards to Speed freaks comments how often do the valves give up? does it matter if the motor was abused or not taken care of very well? Or is it just one of those things common to the motor? Also I have a very large turbo (T4 60 trim) that will be going on this summer, are there any throttle bodies that delete the IAC that I can buy instead of buying the $200 IAC in preperation for the turbo? Again thanks for all the help!!
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