My Isspro tach used to read 750-800 at idle in Drive, with A/C. Cruising at 75 would go to 2000 RPM. I had a tire malfunction which caused extensive damage to the wheel well and bed area, and now my rpm's have gone down to 500 in Drive, with A/C. Cruising to WOT, and the best it'll do is 1500 rpm.

Is there something in the rear that might have gottten damaged that is related to the tach?

 

I have an Isspro tach, and I have a heck of a time with the connections. They must be tight, or the tach just doesn't work right. Mine acts differently than yours, it reads zero rpm at idle and then straight to 2000 rpm upon acceleration, but it still wouldn't hurt to check the connections (if you haven't already!). I also put a little bit of dielectric grease on the connections the last time that the tach acted up. Hope this helps!

 

I'd check the fuel lines from the tank, the return to the tank, and the vent line to make sure they haven't been squished.

Regards, DBF

 

Does the engine sound different? (at 500rpm, it will want to die at any time, oil pressure light comes on, etc) If not, I'd say it's in the tach. But, since you say the RPM dropped at cruise, too, that is in the tach, not the pump. Mine is somewhat erratic, but not enough for me to try troubleshooting just yet.

Daniel

 

Thanks for the advice, guys. Here is the list to check:
1. Since I had the rpm's at 750-800, I swithched to POD injectors and Stans 4" exhaust.
2. After the tire malfuction accident, I saw that it tore out the wire harness off my transmission fluid fan cooler, and I saw sparks. maybe a fuse is out which may be tied into the tach.
since I drive the truck only twice a week max, I never noticed if putting pods and stans could have changed the rpm's. Could they have? Also, could someone get it straight on the rpm settings? Is it 750 w/ auto and A/C on, at idle while in drive, or park? FSM says"while in gear". what do you all understand that to mean. Remember, I am automatic. i believe it is 700 rpm's for manual transmission.

 

Bigragu,

Your newly installed POD's will have a higher flow rate. That could cause your drop in idle RPM. Is your full fuel screw cranked up? If not, give it more fuel.

Aloha,
Matt

 

Hey Island Boy! Book 'em, Dano! Bet you get tired of hearing that...anyway, I was getting ready to start a new tread asking if new injectors and an increase in your exhaust size from stock to 4" would INCREASE or DECREASE your engine RPM's? seems that it would increase, being that the engine is given more fuel and exhales better? I'm thinkin' like Fan Laws, and you HVAC guys know what that's all about. Could be wrong in my thought process, though. What do you think, Bolivar, or anyone caring to help me out in this brain stump?

 

Bigragu,

POD's have higher 'pop' pressures than stock sticks. It takes more fuel to make it 'inject' into the cylinders. Give it more fuel. Oh, "Book em, Dano!" has kinda faded out over the years. We still get the reruns of Hawaii 5-0 but nobody uses the phrase anymore. 'Dog the Bounty Hunter' has taken over in this day and age.

Aloha,
Matt

 

Does 4" exhaust make a difference/add to this dillema? Again, what is the recommended spec for the truck in rpm's? The unclear part in the FSM is it doesn't state to have spec'd RPM in D or P gears, it just says "while in gear". There is a big difference between the two.

 

Exhaust will not make a difference. If I recall, in 'drive' with the A/C on @ 750 rpm.

Aloha,
Matt

 

Dude- what are you doing up this late? Thanks for the advice, and I am not complaining. If I was now in Hawaii, I'd be crashed with a belly full of cool coconut milk!

 

It's only 8:52pm Hawaii time. Where are you located? I'm at least 3 hours behind you if you're on the West Coast. And a 'belly full of cool coconut milk'??? That will give you major diarrhea!

Aloha po (good night),

Matt