Starting Rough, Running Rich?

5.9Limited · Post by **5.9Limited** » Mon Mar 30, 2009 8:31 am

Hey all. I've a gotta jeep with a 5.9 Liter V8, it runs great, has upgrades but of late its been winding out the starter and starting a little rough, and by the smell of the exhaust its running a little rich, also seen in my mpg as well. I know the starters fine, and if the fuel pump/sending unit had issues, i know it woud affect more than just its starting ability.

Im thinking sensory issue??? o-2 sensors maybe? I already replaced the TPS (throttle position sensor), so maybe map sensor or IAC?? any insights and help is much appreciated.

Post by **stipud** » Mon Mar 30, 2009 9:30 am

No check engine lights obviously?

I don't really know your car, but the obvious culprits would be air intake measuring related. MAF, MAP, IAT, etc. Generally if you have a fuel issue, it's too LITTLE (running lean, or not at all), almost never too much (rich).

O2 sensor faults would almost certainly set a CEL immediately, and would not affect starting, since they typically aren't used until the car warms up.

If I had to take a total shot in the dark across the internet on an unknown car, it would be MAF.

nutxo · Post by **nutxo** » Mon Mar 30, 2009 3:23 pm

Rich when its cold is normal. You pulled the plugs to take a look?

wash with gasoline · Post by **wash with gasoline** » Mon Mar 30, 2009 3:29 pm

dont forget to look for the basics, vacuum leak. also check to see if your check engine light works, ive seen a few unplugged

if you can get your hands on a good scanner you should be able to check to make sure the o2 sensor and tps you replaced is working rite, i learned long ago that just because its new in the box dosnt mean its good. id be leaning towards maf as well

Post by **mr tibbs** » Mon Mar 30, 2009 3:56 pm

What mods have you done and have you chipped it?

dBincognito · Post by **dBincognito** » Mon Mar 30, 2009 3:59 pm

mr tibbs wrote:What mods have you done and have you chipped it?

That's what I was thinking.....those "chips" can lose their electrical values and cause your car/truck/suv to run like crap

Post by **Rold Gold** » Mon Mar 30, 2009 4:45 pm

I was also gonna say plugs/wires/cap/rotor would be my first stop. I know some of the parts stores have a reader that they'll plug in for free...atleast around here they do.

wash with gasoline · Post by **wash with gasoline** » Mon Mar 30, 2009 10:34 pm

x2 on the chips losing there memory, i had a braum brenner? spelling chip go bad in my corrado about a year an a half ago. car still ran, but turned into a gutless pig. changed out the chip and i was back to laying rubber. not shure what happened to cause it, but it deff died

dBincognito · Post by **dBincognito** » Mon Mar 30, 2009 10:41 pm

wash with gasoline wrote:x2 on the chips losing there memory, i had a braum brenner? spelling chip go bad in my corrado about a year an a half ago. car still ran, but turned into a gutless pig. changed out the chip and i was back to laying rubber. not shure what happened to cause it, but it deff died

The "chips" are nothing more than resistors that are fooling your computer....the air intake temperature sensor measures the air temperature by it's electrical value...there is no thermometer in your airbox

The "chips" are resistors that are set at pre-set values tricking your computer into thinking that the air coming into the engine is colder than it really is...this tells the computer to remap the air/fuel ratio curve...thus making your car run faster.....but not exactly healthy......bust 1 of those "chips" or "performance control module's" apart and the inside is a joke

Over a period of time those resistors tend to lose their values which will cause the car to run in open loop mode.....after that there is too much to explain

Post by **stipud** » Tue Mar 31, 2009 7:24 am

dBincognito wrote:The "chips" are nothing more than resistors that are fooling your computer....the air intake temperature sensor measures the air temperature by it's electrical value...there is no thermometer in your airbox

The "chips" are resistors that are set at pre-set values tricking your computer into thinking that the air coming into the engine is colder than it really is...this tells the computer to remap the air/fuel ratio curve...thus making your car run faster.....but not exactly healthy......bust 1 of those "chips" or "performance control module's" apart and the inside is a joke

Over a period of time those resistors tend to lose their values which will cause the car to run in open loop mode.....after that there is too much to explain

Wellllll...... that's not right.

$5 Ebay "chips" certainly are MAF resistors like you suggest... and they are total bullshit, that only make your car run worse. Using resistors to trick your car to run faster is a good way to throw things out of whack completely, possibly causing engine damage.

But a real "chip" tune is a different ECU or EPROM, which is a lot more than just a resistor... it's a full blown new set of tables/lambda adaptations/torque request maps/etc.

Also, resistors losing resistance over a couple of years is absurd. If it did, your car would run better, because you wouldn't be tricking your sensors anymore. If anything though, the things are so poorly constructed, it would fall apart, and disconnect your sensor completely. Also bad.

dBincognito · Post by **dBincognito** » Tue Mar 31, 2009 7:39 am

The only real chip is 1 that goes inside your ECU...i.e Hypertech, JET Reflash

If it's not a stand alone system it's a waste of time

Performane Control Modules such as JET, or Venom....are a joke..open them up..I have seen very few "Chips" or "Performance Control Modules" that actually do something.....if it doesn't go direclty into the ECU...it does nothing

Stipud I will spend $20 to prove you wrong on the resistors losing their value....I have measured them

You can also use resistors to trick other devices in your car....you can turn your stock fuel pump into a high flow fuel pump with 2 simple resistors.

Post by **kg1961** » Tue Mar 31, 2009 7:50 am

When did you change the fuel filter,spark plugs wire, cap rotor?
I would look into these things before I think its something with the ECU
Did you just get gas? maybe bad gas. I only use shell gold in all my cars.
If you don't drive it much or long times maybe carbon build up

wash with gasoline · Post by **wash with gasoline** » Tue Mar 31, 2009 8:48 am

the chip i had go bad was one that goes in the ecu, not the $5 ebay jobs.in the past when these have gone bad in other cars the checkengine light comes on and it goes into limp mode, or just dies on the road. with this one it kept running, no light just turned into a dog. dont know why. as far as the jeep goes id check out all the tune up stuff, vacuum leaks before blameing the ecu, unless u have the original chip and its easy to change you could try swapping it back to see if the problem goes away

5.9Limited · Post by **5.9Limited** » Tue Mar 31, 2009 11:49 am

I used to have a jet chip but it went bad...it was making my engine throw a code and was sending signal to my tps that was bad, making the ecu think I was at full throttle all the time... so i junked the chip and won't replace it. I've had problems ever since then, minor ones. I had new (rebuilt) injectors put in at the same time I took the chip out, so I thought I got crap injectors but I had 'em checked and they were fine.

I bought new plugs about a year ago < Bosch Platinum 4's... so they should be fine, but I guess I'll check em, I also replaced the coil last year with an Accel 45k volt upgrade coil, with Taylor 8.2 mm thundervolt wires...very nice wires. I haven't don'e anything with the distributor yet, so I'll chekc the cap I guess.

its kinda quirky for sure...sometimes it winds out the starter like I said, other times its like it starts too fast, doesn't even turn over once and BOOM it starts and rumbles its way to a smooth idle... and if you start it after its been run a while it usually starts great after running forsome reason....any more clues????

Post by **stipud** » Tue Mar 31, 2009 11:53 am

Could be something like the crankshaft/camshaft position sensor as well.

Really impossible to diagnose these things without at least some experience with the car. Have you tried a Jeep forum?

dBincognito · Post by **dBincognito** » Tue Mar 31, 2009 11:59 am

stipud wrote:Could be something like the crankshaft/camshaft position sensor as well.

Really impossible to diagnose these things without at least some experience with the car. Have you tried a Jeep forum?

I think more info is in order too....what mods have been done...is the Jeep maintained ? Did you do anything recently with it ? etc....

5.9Limited · Post by **5.9Limited** » Tue Mar 31, 2009 2:58 pm

I think more info is in order too....what mods have been done...is the Jeep maintained ? Did you do anything recently with it ? etc....

mods...well the ignition upgrades I discussed earlier, aem brute force intake, throttle body spacer, new injectors, full 3" catback exhaust system...had the jet stage 2 chip but ditched it...

care/maitenance : the jeep has 147,000 miles, I bought the vehicle from the 2nd owner, who's father was the 1st owner, have most records of work since '98...the jeep has always run synthetic oil, the last owner was an amsoil dealer so that what he was running, I run mobil 1... I change the oil myself before the recomended milage. I run all synthetics in my transmission, front and rear diff's, have a hanson transmission cooler (I tow) and being a detailer the engine compartment stays very clean. and no I haven't done any recent upgrades or changes. this help?

yeah IM a member on 2 jeep forums but have had NO LUCK. apparently they're all too cool to help out the new guy...they'd rather stay their small circle of hoyty toyty jack-asses. so I gave up those a while ago.....

oh by the way. you guys rock

dBincognito · Post by **dBincognito** » Tue Mar 31, 2009 3:24 pm

5.9Limited wrote:
I think more info is in order too....what mods have been done...is the Jeep maintained ? Did you do anything recently with it ? etc....
mods...well the ignition upgrades I discussed earlier, aem brute force intake, throttle body spacer, new injectors, full 3" catback exhaust system...had the jet stage 2 chip but ditched it...

care/maitenance : the jeep has 147,000 miles, I bought the vehicle from the 2nd owner, who's father was the 1st owner, have most records of work since '98...the jeep has always run synthetic oil, the last owner was an amsoil dealer so that what he was running, I run mobil 1... I change the oil myself before the recomended milage. I run all synthetics in my transmission, front and rear diff's, have a hanson transmission cooler (I tow) and being a detailer the engine compartment stays very clean. and no I haven't done any recent upgrades or changes. this help?

yeah IM a member on 2 jeep forums but have had NO LUCK. apparently they're all too cool to help out the new guy...they'd rather stay their small circle of hoyty toyty jack-asses. so I gave up those a while ago.....

oh by the way. you guys rock

In my experience, there is very little knowledge to be had in car forums.....I'm a member of ToyotaNation.com....that place is a joke.....I tried asking about swapping my 94 Corolla over to quad throttle body's and they were all laughing, and trying to tell me that parts that are directly interchangeable were not

.....we will see who is laughing in a few months when I post pics of the whole process

5.9Limited · Post by **5.9Limited** » Tue Mar 31, 2009 4:07 pm

I feel the same way...I figure they're such jerks and won't help ya because they don't know a throttle body from their a$$ and don't want to admit it.

Post by **mr tibbs** » Tue Mar 31, 2009 4:21 pm

You probably want to check those plugs. I used to run them, until I found out my car really didn't like them. I had them in my '97 4Runner with no problems, then when I got the Saturn I tried them in there. Nope, not happening, I could seriously feel the power loss (even in the Saturn). Then my old man tried them in his '05 Tacoma, same thing, not happening. It seems they work well in some motors, and horribly in others. I would swap them out with the cheaper "V" plugs and see if there is a difference.

Also, you might want to try and have the vehicle scanned even if it is no throwing a CEL. There still might be a code in there that will tell you what is going on.

dBincognito · Post by **dBincognito** » Tue Mar 31, 2009 5:26 pm

mr tibbs wrote:You probably want to check those plugs. I used to run them, until I found out my car really didn't like them. I had them in my '97 4Runner with no problems, then when I got the Saturn I tried them in there. Nope, not happening, I could seriously feel the power loss (even in the Saturn). Then my old man tried them in his '05 Tacoma, same thing, not happening. It seems they work well in some motors, and horribly in others. I would swap them out with the cheaper "V" plugs and see if there is a difference.

Also, you might want to try and have the vehicle scanned even if it is no throwing a CEL. There still might be a code in there that will tell you what is going on.

I won't run anything other than NGK's.....I'm stubborn

Post by **Rold Gold** » Tue Mar 31, 2009 5:30 pm

NGK for life in all my Honda's. Ya might see what they put in the motor from the factory and try those. Bosch plugs don't work right in all cars..........

dBincognito · Post by **dBincognito** » Tue Mar 31, 2009 5:37 pm

FuzzyHoNutz wrote:NGK for life in all my Honda's. Ya might see what they put in the motor from the factory and try those. Bosch plugs don't work right in all cars..........

You know what's funny...my gf's mom's 02 Elantra suggests NGK Iridium's in the owner's manual

Post by **mr tibbs** » Tue Mar 31, 2009 6:07 pm

NGK or Denso in the Toyota's from here on out. After the fiasco with the Bosh Platinum Plus 4's in the Taco I see no reason to wander from OEM anymore.

Post by **stipud** » Tue Mar 31, 2009 6:25 pm

Yep, spark plug is often very important to keep in stock spec.

For example, my engine uses them to measure ionization in the chambers to get a richer burn. If you use the wrong plugs, it throws it all out of whack, and the car has no knock protection.

Try stock sparkplugs (check your manual). Worst case scenario, if it's no better, you can put your Bosches back in, and keep the stock ones for your next change.

Starting Rough, Running Rich?

Starting Rough, Running Rich?

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