TPS/O2 Sensor Codes

[jameskuzman]

Hi all -

I posted a few days ago about a hard-stating-when-warm problem with my '85 LeSabre after rebuilding the carb (E4MC).

Since then, the SES (Service Engine Soon) light has come on, and in addition to the warm start problems, it's taken to idling too fast when warm.

I pulled the codes tonight at got a 22 (TPS Voltage Low) and a 45 (O2 Sensor - Rich Exhaust).

Would a bad TPS cause the high idle, rich exhaust, and/or no-start problems?

I'm going to replace it regardless, I think, but was just curious to know if it might be the cause of all of the symptoms.

Thanks much,

Jim

[Cliff Ruggles]

The TPS has no control over fast idle when cold, curb idle speed when hot,  or how well the engine starts.

If you are having cold start issues, check the choke and the accellerator pump, and make sure they bowl isn't dry from leaking bottom plugs.

The choke pull-off unloads the choke flap on cold starts, and the fast idle speed is controlled by the adjustment screw on the passengers side of the carb under the choke housing.......Cliff 

[jameskuzman]

Thanks Cliff!

Cold starting is actually ok now.  It sets up on fast idle by opening the throttle a bit (warm down here!), starts well, and runs very smoothly. The choke opens just enough and releases progressively over the course of a minute or two.  No issues there other than the fact that blipping the throttle does not bring it down from the highest step on the cam to second highest.  Fast idle speed does drop down as the choke opens, though.

The real problem is warm starting after the car has been sitting for an hour or so.  It acts as though it's not getting fuel at all.  Reminiscent of the old vapor lock, actually.  If it's only been a few minutes, it fires right up.  Otherwise, it cranks but won't catch.  Doesn't even sound like it's TRYING to catch.  Then, out of the blue, after waiting another hour or so, it fires up as soon as I hit the key...

Thoughts?

Jim

[jameskuzman]

Cliff, I should add that the high curb idle is unusual in that the throttle doesn't even contact the tip of the curb idle screw, so there's no way to adjust it down. Wondering if it got bent at some point, but I can't recall any point in the rebuild when that would have happened.

Jim

[jameskuzman]

As an update to the thread, I pulled the carb off the car last night and found the bowl was full of fuel after sitting for 3 days - so I think we can say any hard-starting issues are not related to drain back or leakage.

The accelerator pump was squirting fuel when I pressed the plunger, so that's working ok, too.

I'm going to replace the TPS in the next few days because of the code it keeps throwing.

As far as the high curb idle, the throttle is not closing against the adjustment screw even when it's all the way out, and the primary plates are open just under 1/8" when the throttle should be closed.  I can see that it's being kept open by a tab that rests against the fast idle cam on the choke side of the carb.  It's on the lowest step, but that's definately what's keeping the throttle open and causing the high idle. 

Suggestions (other than bending this tab, unless that's what you're really supposed to do) on getting the throttle to close all the way are welcome.

Ditto any thoughts on what's causing the no-start condition after the vehicle has been sitting an hour or so. 

This was NOT a problem before the rebuild, so I immediately looked to something I did wrong with the carb first, but I'm wondering if that's a red herring and the problem is coincidental and possibly electrical in nature....?

Thanks to all,

Jim

[Cliff Ruggles]

At curb idle there shouldn't be any contact between parts on the choke side of the carb as far as the secondary cam and any parts on the shaft.....Cliff

[jameskuzman]

Well...

I learned a few things over the weekend when I took the carb back off to replace the TPS.

The first thing I learned was that the low-voltage code probably wasn't due to a bad TPS at all (although I did replace it since I was in there) - it was caused by my inexperience and carelessness.

I neglected to re-install the little silver plunger that goes through the airhorn to connect the accelerator pump lever and the tip of the TPS when I reassembled the carb.  Essentially the TPS wasn't active in the circuit at all - there was nothing TO activate it.  

The second thing I discovered was that the issues of the curb idle being high, the throttle not contacting the curb idle screw, the inability to "blip" the throttle and get the engine off fast idle, and the hard-start problems when hot were, I believe, quite related to one another and were also due to inexperience.

The lock-out lever on the choke side that keeps the secondaries from opening until the engine is warm (and also rests against the fast idle cam) was in backwards.  This was opening the throttle from the choke side (high idle, no contact with curb idle screw) and was keeping the cam from falling down from the high step until the choke opened fully.

Since it was also keeping the primaries slightly open when the car was turned off, my theory is that either heat from the manifold was rising up through the openings and percolating the fuel, or fuel was actually dripping down into the hot intake manifold, causing a flooding condition after the vehicle sat for awhile.

I flipped the lever over (and had to "go fishing" to get the choke rod back on the choke screw - fun!), put the carb back on, and every single issue has disappeared.  

Lessons learned :-)

Jim

[Cliff Ruggles]

Good news, and part of the "learning curve" with carburetor repair.  Been there about a million times, and still learning!......Cliff