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voyager flat spot

  #1  
Old 08-14-2009, 04:30 PM
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Default voyager flat spot

hi all

my 98 r reg 2.0 litre voyager has a bad flat spot at about 2,500 rev,s it ticks over fine but when you rev it up it starts popping i have checked the plugs and they are black ive tried replacing them and no differance when i drive the car it holds back and sometimes i have to keep the revs up at traffic lights and road junctions other times it ticks over ok i have a timing strobe light and tried it on each plug lead and there seems to a problem on numbers 2 and 3 cylinder the flash on those is not consistant and goes in time with the flutter of the engine im thinking it could be a dodgy coil pack or leads

what do you guys think
thanks in advance

pete.......................................
 
  #2  
Old 08-14-2009, 04:52 PM
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The black indicates either an overly rich mixture or incomplete combustion. As you have identified cylinders 2 and 3 as having an erratic spark the logical path is

1. Replace disi cap, rotor arm,(don't know if your car has these) HT leads and HT coil
2. Check timing (may not be possible depending on system)
3. Check injectors
4. Check compression on cylinders 2 & 3

Question, what colour are the plugs on 1 and 4

Thing with modern cars is that timing is typically controlled by the ECU and is based on the Crankshaft position sensor, Throttle position sensor, and Manifold absolute pressure sensor. These 3 sensors feed info back to the ECU which then uses MOSFETS to de-energize the primary winding in the HT coil to send the spark. Ignition coils don't seem to last as long these days as the old oil filled ones.

I would start with the HT coild and leads. You can use a est meter to tes the resistance of the cables. Compare them with 1 & 4.
 
  #3  
Old 08-15-2009, 05:37 AM
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hi glowplug

thanks for getting back my car has no dizzy cap its a coil pack all 4 plugs are black i will check the resistance of the the leads and check the compressions but the spark is very erratic on no,s 2 and 3 plugs the car ticks over perfectly but as soon as you rev the engine it starts misfiring at about 2.500 revs and i found out by using a strobe gun on each lead that there is a erratic flash on those leads i mentioned which coincides with the erratic running of the engine which makes me think the coil pack is breaking down how do i check the injectors ?.

also the service light does not indicate a fault as go,s out stright away surly if there was a fault on any of the sensors it would throw the light on

pete.....................................
 

Last edited by [email protected]; 08-15-2009 at 05:45 AM.
  #4  
Old 08-15-2009, 02:31 PM
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I would start with a new HT coil. Testing fuel injectors involves removing them, checking the spray pattern and measuring the amount of fuel delivered in a period of time. At this stage I would say the HT coil is suspect especially as the situation worsens as revs increase. A weak spark will be noticeably worse as the fuel load upon the affected cylinders is increased.

You could of course just check the earthing between the coil and the engine as well as between the engine and the body. A floating ground will also give spurious behaviour, however my money would still be on a duff coil.

Another thing to check is the actual spark delivered as well. Simply remove all 4 plugs, insert them into their respective plug leads and rest the metal part against the engine in suc a way that you can see the spark gap. Then get someone to crank over the engine whilst you watch the plugs. Each should give a good healthy blue spark. This is assuming that all plugs are gapped corectly.

I did not say there was anything wrong with the sensors, I was just explaining how cars without distributors provide the spark in the correct sequence and time.
 
  #5  
Old 08-15-2009, 04:31 PM
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hi glowplug

thanks for your reply

well after doing a few checks i decided to replace the coil pack together with the leads after initial start up the engine flutterd a bit then after a few revs of the throttle getting it up to 2,500 revs it all cleared and the engine was running perfect i tried the car round the block and all was well i left it ticking over for a while then gave it a few revs and the problem was gone so the problem was the coil pack after all as no,s 2 & 3 plug run from the same part of the coil pack my guess is that part was breaking down slowly

thanks for all your help

all the best

pete..........................................
 
  #6  
Old 08-15-2009, 04:33 PM
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You are most welcome, glad you are up and running again.
 
  #7  
Old 08-15-2009, 04:38 PM
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thanks agian glowplug

this is a great forum im new here and would recommend it to anyone

pete..............................
 
  #8  
Old 08-19-2009, 04:10 PM
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problems back ive been told from a voyager expert that it could be the map sensor

pete.........................
 
  #9  
Old 08-19-2009, 04:18 PM
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Bummer dude

Could be but a vaccum leak will also cause the MAP sensor to go funny. Check all your vaccum pipes for any signs of perishing or cracks.
 
  #10  
Old 08-19-2009, 04:52 PM
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hi glowplug

ive checked all the vacuum pipes and they all look ok i was checking them to see if any one of them was cracked when trying to find out why my cruise control was not working.

ive since been told by the same guy that it could be the clockspring and he told me about the recall i checked my cars vin no and it has,nt been done so the car is now booked in to chrysler to have the mod done hope it works but it still does,nt fix the flat spot

pete..........................
 

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