[S.A.E.92rolla]

hey guys i know you all will have a blast with this one but i cant seem to figure out the problem area on my 4 AFE!

The car idles great. I can up the throttle and the rpm will increase with out any break or hessitation in increase while idleing. NOW when under a load ( in drive or reverse) under any acceleration the car hicups randomly in 1st , 2nd and 3rd gears. From about 700 accelerating up to about 3000 rpm it does this hic up randomly then when it hits 3000 it sounds good and accelerates with no hessitation up as high as i want to take it.

I have changed the spark plugs, fuel filter cap rotor and wires in the last 1000 miles and this did not start happening untill after i fixed the fuel filter. which leads me to beleive its a fuel pump, or filter, or the strainer for the pump... IDK. before i start tearing into anything major i thought i would ask to see if maybe someone was experiencing the same type of problem.

Also,,, got curious and pulled the back seat up to reveal the little acces panel over the fuel tank. wires go into it and its 2 bolts that hold the panel on then under its about 7 bolts to get to what i thought was the fuel pump assembly and pump and strainer but pulled out what looked to be the fuel sending unit and the little lever to measure the amount of gas. Were the hell is the fuel pump and strainer any ideas???


Sorry bout the huge post but any help is appreciated guys.

 

[SuperRA]

My slightly educated guess is that it has something to do with the Throttle Position Sensor, TPS for short.

 

[Donald]

You need to drop the tank to get to the pump. It is further back.

Try swapping out the MAP sensor if you can get one to borrow. I just had a similar problem and swapping out the map sensor fixed it. My symptoms were not identical, but similar.

It woold hickup intermittently, and would die when I put it into reverse, but idle quite smoothly otherwise.

 

[90 GP]

Did you try checking for stored check engine light codes? Sometimes they are stored without setting off light. This link tells how to do it and what they mean. Also check the vac line to the MAP sensor for leaks.


http://www.troublecodes.net/Toyota/

 

[S.A.E.92rolla]

changed all the vacuum lines today and engine still has the same symptoms only now that there are no vacuum leaks the hessitation is still noticable. also i would like to add that in any gear there is a serious lack of power especially at 3000 in 3rd gear its almost like it hits a plateau.

ideally if i unplug the map sensor and run the engine will it sound the same if the map sensor is bad? basically im asking if the map sensor does not work at all if it burns out or if it reads all messed up to the ecu? trying to figure out how i can test mine, without buying there 300 plus $. junkyard? any way to tell if there any good?


diagnostics--- in the plug in the engine bay i tried to bridge 2 terminals that it calls for but there was some grease or somethin couldnt tell if it was dialectric grease or not but couldnt seem to get the paper clip to contact for some reason.


im keeping at it and ill let yall know the deal

 

[Donald]

The test for the map sensor involves getting access to the ECU connectors, with them still plugged into the ecu, and doing a voltage reading with vacuum on and off (stupid setup if you ask me).

You would think just doing an ohm meeter reading at the sensor would do, but no it doesn't work like that.
I tried that to compare a known good one with a suspect unit, and the readings were the same.

I have had good results with MAP sensors from the junk yard.

Bridging the connectors in the check port can be a pain. That grease is dielectric grease, but they still seem to corrode, so the first time might require a lot of patience and many trials.
It is hard to locate the contacts also, you might get the paper clip into the hole and not find the contact.

Keep trying

I am guessing that you don't have a workshop manual.

My suggestion to anyone wanting to do their own car maintenance is "Get the manual"
The Toyota manuals are not cheap, but worth it. They cost less than an error could possibly cost you.
At the very least, get a haynes manual. They only cost about $20.

 

[90 GP]

The paperclip doesn't make the best connection to bridge the terminals. I made a jumper with two small U shaped solderless connections ( found in electrical dept of auto parts stores or Home depot) and a length of small gauge wire. I broke of one side of each of the U shaped connector and they fit squarely in connections of diagnostic port. To connect the U shaped connector to the wire crimp it with pliers and put electrical tape around connections.

 

[Donald]

The paperclip doesn't make the best connection to bridge the terminals. I made a jumper with two small U shaped solderless connections ( found in electrical dept of auto parts stores or Home depot) and a length of small gauge wire. I broke of one side of each of the U shaped connector and they fit squarely in connections of diagnostic port. To connect the U shaped connector to the wire crimp it with pliers and put electrical tape around connections.

:thumbsup:

Good idea!

 

[S.A.E.92rolla]

fixed the hicup turned out to be the 4th cylinder spark plug boot. Inside the boot the female piece that is crimped to the wire came unhooked from the wire and was stuck on the plug. So under 3000 rpm the spark was not big enough to jump to the female piece but above 3000 the spark was so great i guess it jumped to the plug causing it to kick in which describes why i was having those symptoms. Either way thanks everyone that gave me their input.