Hey everyone... I don't have a Buick, but I have a 1987 Cadillac Brougham with the 307 olds engine and a Rochester e4mc carb... I had to replace the TPS in the carb and now my car doesn't work. It starts and runs...I can rev the engine fine in park...The problem is when I try to drive it. If I keep light on the throttle the car goes, but very slow. If I push down hard on the throttle the engine does nothing. No revving. It seems like it's about to die, infact. Maybe getting choked? not sure... I also noticed while looking into the problem that there is some gas leaking from the fuel inlet, but I didn't even touch that area of the carb while replacing the TPS. I've ordered a new fuel filter anyways so I will look at the inlet when I put that new filter in, but any other ideas what could be wrong? Please help me! :ball:
Call autozone , tell them you just bought a tps and you need to know what voltage to set it to. It should be in the computer with the instalation instuctions. There is a positive wire connected to the tps that you can tap into. Loosen the screws on the tps. Read the voltage off that wire. On my cars it has been the wire in the middle. Do not cut the wire just tap into it. Twist the tps and the voltage will go up ore down.:TU:
All the sensors on your engine work the same way. They receive a 5 volt reference signal from the computer. The sensor modifies the signal based on what it is reading, and sends that back to the computer. The TPS is a throttle position sensor. If I remember correctly, closed throttle should be about .42 volts. Wide open throttle is about 4.5 volts. There are 3 wires leading from the sensor. One is the reference wire (5 volts), one is a ground, and the 3rd is the signal wire. You can back probe the wires with a voltmeter and figure out which is which. Connect the voltmeter between the signal wire and ground. To adjust the TPS, you must drill out a plug in the top cover. The plug covers a very small hex. It takes a special tool to turn the hex to adjust the TPS. If the carburetor has ever been rebuilt, there is a good chance the plug has already been drilled out. This will help, http://tlentz.oldsgmail.com/howto.html#TPS http://www.restockit.com/GM-Compute...0F1&Bvar7=100F1&ci_src=14110944&ci_sku=THX362
Thanks man, that first link gave a really down to earth explanation of how to set the TPS. Will have to pick up a new multimeter and try this this weekend. :beer
I suspect two things here. First, did you remember to replace the little green plunger under the accel pump link? This link drives the tps, and if missing, the computer won't know that the throttle is moving. Second, did you remember to re-connect the mixture control solenoid on the pass-side of the carb? If you did not, the engine will run very rich, all of the time. Emissions engines are very sluggish if run rich. Does the check engine light illuminate with the engine off, key on? This light should have signalled an issue after a short period. Ray
Well, the problem turned out to be that the TPS somehow broke inside of the carb. I've ordered another TPS and will put it in once it comes in. Someone suggested that I use a putty knife to hold the TPS in place while putting the top of the carb back on, then remove the putty knife before tightening the top. Anyone have experience installing a TPS in these carbs? Just wondering if this will work and/or if you have any better suggestions?
The putty knife trick works well. Do you know how to check the sensor after it is installed? I ask because after you install a couple of the screws, you can check the sensor using the multi-meter. Four screws installed in the air horn will secure it sufficiently to check. Be sure also not to bend or misplace the primary metering rod actuator or the rods. It may be wise, once the throttle position sensor is installed to check the dwell on the mixture control solenoid. It should move slowly between 20-35 deg at idle and at 3000 rpm. The tps will cause the dwell to suddenly drop, then return if it is working correctly. For the record, these engines were notorious for a leaking cannister purge valve, causing the engine to ingest sufficient fuel at idle to peg the meter at 55+ deg. If it is stuck at one end or the other, let us know... Ray
Thanks Ray. When the new TPS gets in I will put it in. I do have a question...can anyone show me where the "plug" covering the TPS adjusting screw is located?
The TPS is easily broken on those carbs when the top goes on. Use some bearing grease on the pin to keep it in the airhorn during re-assembly, it will not slide down and cause troubles. I also like to slot the end of all of the adjustments with a fine hacksaw blade, then tap the airhorn access holes and install 1/4-20 set screws. This makes fine tuning much easier with a small flat blade screwdriver once it's back together. A neat trick to turn the TPS screw is to drive a very small roll pin over it with another roll pin welded to it to make a "T" handle. The Computer Controlled carburetors are capable or great performance, and the Computer only controls the part throttle A/F ratio. It's also easy to "trim" the fuel curve by controlling the metering rod height even with the M/C solenoid and TPS unhooked. We have set up quite a few of them for later model Firebirds, Camaro's and Monte Carlo SS's to work with large CID roller cammed engines and still meet emission requirements with all the factory parts in place and operational. Some of these cars run into the 11's in street trim, but not for long as the 7.5/7.625" differentials last about as long as it took me to type this!......Cliff
The plug you reference is on the back side of the mounting tangs holding the accel pump arm. If you look at the driver's side of the carb, where the accel arm is located, you will see a small, shiny"dot", different from the rest of the tang. The adjuster is behind that plug. I typically use a very small drill bit, and drilling carefully, I make a small hole for a self-tapping screw, which either shatters the plug, or allows me to pull it out. You adjust for exactly .45 volts, when measured to ground. There are three wires on the connector, one for the supply voltage, (5) volts, a ground connection, and the third is the signal voltage to the computer to allow it to know where the throttle is. This third wire is what is adjusted, using the screw behind the plug, to the specified voltage. Make damn sure that everything affecting the idle is right on the money before making this adjustment, including the choke being off, the timing is correct, and the idle is EXACTLY as specified. Let me know... Ray
Yes, it is on the rear most tang, closest to the choke housing. In the photo, it is just below the top of the tang. In this case, it appears to be more of a depression in the tang, but that is what you seek for adjustments. Ray
Is it the part circled in red? Sorry for all the questions, just want to make sure I don't drill the wrong thing.
Larry, that picture helps me out A LOT! Thank you so much! When I get home I will look at it and if I still can't find it with that picture (doubtful, thanks a lot ) then I will take a pic.
The circle shows the area housing the air valve pivots. The accelerator pump arm is the one connected to the primary side of the carb, next to the choke housing. This arm, attached to the carb using a roll pin, pushes on the accel pump through the external linkage using the exposed link. Operate the throttle linkage, and you will see an arm moving counterclockwise, pushing down on tha accel pump, using the arm next to the choke. On the two ears protruding vertically from the air horn, one is close to the choke housing, and the other is farther away. On the ear closest to the choke housing, barely visible above the accel pump arm in the picture, you will see a shiny point, about 1/4 the size of the one circled, aimed almost exactly at the wiper motor when the carb is installed on the manifold. Is there any way I can edit your picture to move the circle forward? One other way I have is to scan a picture from a Rochester book, and attached it to a reply. Any one willing to help here? Both Matt and I would appreciate it. Ray
The circle shows the area housing the air valve pivots. The accelerator pump arm is the one connected to the primary side of the carb, next to the choke housing. This arm, attached to the carb using a roll pin, pushes on the accel pump through the external linkage using the exposed link. Operate the throttle linkage, and you will see an arm moving counterclockwise, pushing down on tha accel pump, using the arm next to the choke. On the two ears protruding vertically from the air horn, one is close to the choke housing, and the other is farther away. On the ear closest to the choke housing, barely visible above the accel pump arm in the picture, you will see a shiny point, about 1/4 the size of the one circled, aimed almost exactly at the wiper motor when the carb is installed on the manifold. Is there any way I can edit your picture to move the circle forward? One other way I have is to scan a picture from a Rochester book, and attached it to a reply. Any one willing to help here? Both Matt and I would appreciate it. Ray
