99 tahoe - trouble starting

[ryank99]

hey guys, new to the forum and the tahoes. i just recently bought a 99 tahoe and im have trouble getting it started. i havent scanned for codes yet, i just wanted to get help on where and what to look for. so heres what happens...the truck will only start if i push the gas pedal to the floor, even then, it still struggles to start. i have to keep my foot on the gas pedal a little bit to keep it running. after a while it will run on its own (without my foor being on the pedal) help please!

 

[SunlitComet]

Usually no starts or a sign of fualty crank sensor or Engine coolant temp sensor, disconnected wiring or a fuel stoppage somewhere. as you describe it it sounds like a fualty sensor maybe even the engine coolant sensor used by the computer. When it is running is the engine light on? Scanning for active or history codes would be good right now. Can you measure the resistance on the temp unit? Located ont the thermostsat housing-two wire plug and with the truck cold and the approximate temperature outside of the truck when you do please?

 

[ryank99]

yeah, the check engine light is on. i got a hold of a scanner today, so thats first on my list for tomorrow along with checking the fuel pressure. coinsidently,i notice my temp guage wasnt reading right (or at least it doesnt look normal to me) so i was planning on changing the coolant temp sensor also. man, that would be great if its a simple fix like that. thanks man, i'll let you know what my findings are...

 

[SunlitComet]

Note. gauge temp is provided by a different sensor not the one the computer uses. I am stoked, scan now scan now

 

[ryank99]

hmm...well, i already bought it so i might as well change it (it was only $13) so where would the sensor for the temp guage located? im anxious about scannin the truck too, i have to wait til tomorrow though....we're out of town, brought the kids to see the grandparents....anyway, i'll let you know, i need to get this thing fixed, my wife already doesnt like the fact i bought it, now the damn thing dont work

 

[SunlitComet]

LH Cylinder Head, near #1 Spark Plug

 

[ryank99]

sorry for the delay. so i got the truck started, whoo-hoo! i ended up changing the temp sensor,cap,rotor,spark plugs and wires and i cleaned the IAC. i also scanned for codes and came up with (2) codes - P0118 and P1345.
not sure the cuase of the P0118. the P1345 i found is either the crankshaft sensor or the camshaft sensor. i meter and tested the crankshaft sensor and its good. so , i'm assuming the camshaft sensor is the culprit for that P1345 code. But wait, theres more! i tested my fuel pressure, its good and within specs BUT it doesnt hold pressure after the truck is turned off...it drops off within seconds. so that leads me to believe that the fuel pump check valve is bad or the spider injectors are leaking. any thoughts,advise or solutions?

 

[SunlitComet]

http://www.sunlitcomet.com/pdf/automotive/tahoe/98-99/1999-Tahoe-p0118.pdf

http://www.sunlitcomet.com/pdf/automotive/tahoe/98-99/1999-Tahoe-p1345.pdf

Clear the codes. Monitor the truck with scanner from a cold engine to eye the engine temperature to see if it climbs as would be expected from warm-up. If the scanner reading for engine temp stay the same high or low then go thru the link for that 188 above. Most likely this what was wrong to begin with. If it comes back then there is a wiring short on that sensor circuit. As far as the 1345 goes read this link follow the info and it will lead the way. The test result will tell you if the either sensor is bad or the distributor alignment is off a little. It looks like you have made good progress so far.

With the gas pressure is that measure with ignition on but engine off with out ever starting?

If the engine runs smooth with no power issues, hesitation, backfires, misfires, etc. after clearing up any code faults I would not suspect the spider just yet. In short you would need to put that pressure gauge in place of the fuel filter to check that valve. But below is the whole diagnosis chart if you want to read it.

http://www.sunlitcomet.com/pdf/automotive/tahoe/98-99/1999-Tahoe-Fuel-Sytem-Diagnosis.pdf

I personally don't worry about the check valve because the initial turn on of key provide a 2 second pressure prime. If the check valve was a failure it would let the fuel in the line drain back into the tank. Mine lets the pressure go after a bit but the fuel remains in the pipes for weeks on end and the priming does its job. IMO


I did have to replace my spider because of some serious problems listed above but it is great now.



Let me know what happens next.

 

[ryank99]

thanks, im gonna have to look into that a little more. as far as the fuel pressure goes, it has about 63psi with ignition on and about 54psi (if i remember right) while the truck is running. the pressure drops as soon i turn the ignition off. it probably drops to about 20psi within around 10-15 seconds. correct me if i'm thinkin wrong, but the reason i wouldnt think it is the spider injectors is becuase with that much pressure loss in that amount of time, i would think that it would smell flooded, which is doesnt.
oh, would me changing the cap and rotor could have misaligned the distributor enough to throw a code? i wasnt rough with it or anything, just curious

---------- Post added at 12:25 PM ---------- Previous post was at 12:16 PM ----------

now that i think about it, my radiator leaks(got a new one coming) so i cant keep my coolant level proper. this could be causing the 0118 code??

 

[SunlitComet]

not really the 118 code is a really for broken connection on the circuit which probably happened becuase it was disconnected while the computer was active. but a low rad could have thrown of your guage sensor and computer sensor reading readings off becuase of the low coolant. Replace your remaining parts, work the 1345 if you can and go back to look things over again for proper operation and go from there. Doing great so far. BTW changing cap rotor should not create 1345 code unless sensor is loose or distributor clamp is loose and out of adjustment or something is really amiss with timing components.